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Diff — Formal power series

Revision #1232 → #2793 · back to history

modifiedFormal seriesa75b04cf774c
FieldFrom #1232To #2793
mathlib.declHahnSeries
mathlib.match_kindgeneralization
mathlib.moduleMathlib.RingTheory.HahnSeries.Basic
noteNo abstract `FormalSeries` in Mathlib; the most general realization is `HahnSeries`, with `PowerSeries`, `MvPowerSeries`, `LaurentSeries` as concrete instances.
statuspartial
modifiedFormal power series88963240bbed
FieldFrom #1232To #2793
mathlib.declPowerSeries
mathlib.match_kindexact
mathlib.moduleMathlib.RingTheory.PowerSeries.Basic
note`PowerSeries R := MvPowerSeries Unit R` is the univariate formal power series type.
statusformalized
modifiedRing of formal power series over Rec3906877b46
FieldFrom #1232To #2793
mathlib.declPowerSeries
mathlib.match_kindexact
mathlib.moduleMathlib.RingTheory.PowerSeries.Basic
note`PowerSeries R` inherits the (semi)ring structure from `MvPowerSeries Unit R` (see `MvPowerSeries.instSemiring`).
statusformalized
modifiedSeries with coefficients [1,-3,5,-7,...]e62fb172aef1
FieldFrom #1232To #2793
mathlib.decl
mathlib.match_kind
mathlib.module
noteIllustrative expository example, not a named object in Mathlib.
statusnot_formalized
modifiedSeries with factorial coefficients1a9bcd564428
FieldFrom #1232To #2793
mathlib.decl
mathlib.match_kind
mathlib.module
noteExpository example (∑ n! X^n); Mathlib has `PowerSeries.exp` (with 1/n!) but not this specific series.
statusnot_formalized
modifiedMultiplicative inverse of formal power series51ff57088b02
FieldFrom #1232To #2793
mathlib.declPowerSeries.invOfUnit
mathlib.match_kindexact
mathlib.moduleMathlib.RingTheory.PowerSeries.Inverse
note`PowerSeries.invOfUnit` constructs the inverse when the constant term is a unit; `PowerSeries.inv` handles the field case.
statusformalized
modifiedDivision of formal power series85cb14dc0f4b
FieldFrom #1232To #2793
mathlib.declPowerSeries.inv
mathlib.match_kindinvocation
mathlib.moduleMathlib.RingTheory.PowerSeries.Inverse
noteDivision B/A is `B * A⁻¹` via `PowerSeries.inv`; a dedicated `Div` instance exists only via the `Field k⟦X⟧` inference over a field.
statuspartial
modifiedCoefficient extraction operator0a7dff49848b
FieldFrom #1232To #2793
mathlib.declPowerSeries.coeff
mathlib.match_kindexact
mathlib.moduleMathlib.RingTheory.PowerSeries.Basic
note`PowerSeries.coeff (n : ℕ) : R⟦X⟧ →ₗ[R] R` extracts the n-th coefficient.
statusformalized
modifiedRing of formal power series in X over Rdc628600d290
FieldFrom #1232To #2793
mathlib.declPowerSeries
mathlib.match_kindexact
mathlib.moduleMathlib.RingTheory.PowerSeries.Basic
noteThe (semi)ring structure on `PowerSeries R` is provided by `MvPowerSeries.instSemiring` transported via `PowerSeries := MvPowerSeries Unit R`.
statusformalized
modifiedFormal power series ring as completionf7d7b1d8cdd2
FieldFrom #1232To #2793
mathlib.decl
mathlib.match_kind
mathlib.module
noteMathlib's `MvPowerSeries/Basic.lean` explicitly notes the I-adic completion characterization is not yet proved (TODO).
statusnot_formalized
modifiedAddition and multiplication of sequences (Cauchy product)9711bf2bc8cf
FieldFrom #1232To #2793
mathlib.declPowerSeries.coeff_mul
mathlib.match_kindexact
mathlib.moduleMathlib.RingTheory.PowerSeries.Basic
note`coeff n (φ * ψ) = ∑ p ∈ antidiagonal n, coeff p.1 φ * coeff p.2 ψ` is exactly the Cauchy product.
statusformalized
modifiedProduct topology on R^N598ee06d4cb7
FieldFrom #1232To #2793
anchor.snippetWe may givethe product topology , where each copy of
mathlib.declPowerSeries.WithPiTopology
mathlib.match_kindexact
mathlib.moduleMathlib.RingTheory.PowerSeries.PiTopology
noteSharpened anchor: original snippet 'We may give' was too vague.
provenanceai-agent1ai-moderated
statusformalized
modifiedI-adic topologyd01e6793b272
FieldFrom #1232To #2793
mathlib.declIdeal.adicTopology
mathlib.match_kindgeneralization
mathlib.moduleMathlib.Topology.Algebra.Nonarchimedean.AdicTopology
note`Ideal.adicTopology I` gives the I-adic topology for any ideal, but its equality with `WithPiTopology` on `R⟦X⟧` is not proved in Mathlib.
statuspartial
modifiedMetric on formal power series7c2331e6de17
FieldFrom #1232To #2793
mathlib.decl
mathlib.match_kind
mathlib.module
noteNo `MetricSpace (PowerSeries R)` instance in Mathlib; only the pi-topology / uniform structure is provided.
statusnot_formalized
modifiedConvergence iff terms tend to 02ef1d1e30e15
FieldFrom #1232To #2793
mathlib.declNonarchimedeanAddGroup.summable_iff_tendsto_cofinite_zero
mathlib.match_kindgeneralization
mathlib.moduleMathlib.Topology.Algebra.InfiniteSum.Nonarchimedean
noteGeneral nonarchimedean-group version exists; specialization to `R⟦X⟧` is not stated explicitly.
statuspartial
modifiedInfinite product convergence7ee95f8a7fab
FieldFrom #1232To #2793
mathlib.declNonarchimedeanGroup.multipliable_iff_tendsto_cofinite_one
mathlib.match_kindgeneralization
mathlib.moduleMathlib.Topology.Algebra.InfiniteSum.Nonarchimedean
noteGeneral nonarchimedean-group version exists; specialization to `R⟦X⟧` is not stated.
statuspartial
modifiedUniversal property of formal power series ring6125359cbd3d
FieldFrom #1232To #2793
mathlib.declMvPowerSeries.aeval_unique
mathlib.match_kindgeneralization
mathlib.moduleMathlib.RingTheory.MvPowerSeries.Evaluation
note`MvPowerSeries.aeval_unique` gives uniqueness of a continuous R-algebra hom sending X to a fixed value; the univariate specialization is `PowerSeries.aeval`.
statuspartial
modifiedn-th power of a formal power seriesbb64ec6abdf6
FieldFrom #1232To #2793
mathlib.declPowerSeries.coeff_pow
mathlib.match_kindexact
mathlib.moduleMathlib.RingTheory.PowerSeries.Basic
noteThe Monoid structure gives `f^n`; `PowerSeries.coeff_pow` computes its coefficients.
statusformalized
modifiedComplex powers of series with constant term 18a3cb3b0c824
FieldFrom #1232To #2793
mathlib.declPowerSeries.binomialSeries
mathlib.match_kindspecial_case
mathlib.moduleMathlib.RingTheory.PowerSeries.Binomial
note`binomialSeries` gives (1+X)^r for r in a binomial ring; general complex-power operator on 1+m·R⟦X⟧ is not packaged.
statuspartial
modifiedInvertibility criterionc6313747e3e7
FieldFrom #1232To #2793
anchor.snippetis invertible inis invertible in [MATH] if and only if its constant coefficient
mathlib.declPowerSeries.isUnit_iff_constantCoeff
mathlib.match_kindexact
mathlib.moduleMathlib.RingTheory.PowerSeries.Inverse
noteSharpened anchor to capture the iff criterion, though [MATH] placeholder remains in-source.
provenanceai-agent1ai-moderated
statusformalized
modifiedGeometric series formula34a41e2c70bb
FieldFrom #1232To #2793
mathlib.declPowerSeries.mk_one_mul_one_sub_eq_one
mathlib.match_kindexact
mathlib.moduleMathlib.RingTheory.PowerSeries.WellKnown
note`(1 + X + X² + …) · (1 − X) = 1`; also `PowerSeries.invUnitsSub` for 1/(u−X).
statusformalized
modifiedDiscrete valuation ring over a field7e08ad5f9976
FieldFrom #1232To #2793
mathlib.declPowerSeries.instIsDiscreteValuationRing
mathlib.match_kindexact
mathlib.moduleMathlib.RingTheory.PowerSeries.Inverse
note`instance : IsDiscreteValuationRing k⟦X⟧` in `PowerSeries/Inverse.lean`, with `maximalIdeal_eq_span_X` giving X as the uniformizer.
statusformalized
modifiedDivision as product with inversec1fb6d2d7a7c
FieldFrom #1232To #2793
mathlib.declPowerSeries.inv
mathlib.match_kindinvocation
mathlib.moduleMathlib.RingTheory.PowerSeries.Inverse
noteDivision reduces to `B * A⁻¹` via `PowerSeries.inv`; over a field a full `Div` instance follows from the `Field` structure.
statuspartial
modifiedCoefficient extraction operator notation7700cba1f4f2
FieldFrom #1232To #2793
mathlib.declPowerSeries.coeff
mathlib.match_kindexact
mathlib.moduleMathlib.RingTheory.PowerSeries.Basic
noteSame as the earlier coefficient definition; notation like `[X^n]` is not scoped in Mathlib but `coeff n φ` plays the role.
statusformalized
modifiedComposition of formal power series96456f62a014
FieldFrom #1232To #2793
mathlib.declPowerSeries.subst
mathlib.match_kindexact
mathlib.moduleMathlib.RingTheory.PowerSeries.Substitution
note`PowerSeries.subst a f` (and `MvPowerSeries.subst`) formalize substitution/composition when `HasSubst a` holds.
statusformalized
modifiedComposition validity conditiondf894633ebc8
FieldFrom #1232To #2793
mathlib.declPowerSeries.HasSubst
mathlib.match_kindexact
mathlib.moduleMathlib.RingTheory.PowerSeries.Substitution
note`HasSubst a ↔ IsNilpotent (constantCoeff a)`; `subst` is only mathematically valid under this hypothesis.
statusformalized
modifiedFaà di Bruno's formula49bed223bb6a
FieldFrom #1232To #2793
mathlib.declFormalMultilinearSeries.taylorComp
mathlib.match_kindgeneralization
mathlib.moduleMathlib.Analysis.Calculus.ContDiff.FaaDiBruno
noteFaà di Bruno is formalized only for iterated derivatives / Taylor composition in analysis, not for `PowerSeries.subst` coefficients.
statuspartial
modifiedLogarithmic series composition example93f52a24c69c
FieldFrom #1232To #2793
mathlib.declPowerSeries.log
mathlib.match_kindinvocation
mathlib.moduleMathlib.RingTheory.PowerSeries.Log
note`PowerSeries.log` exists over ℚ-algebras; the article's specific composition example is not stated as a lemma.
statuspartial
modifiedExistence of composition inversee7dffe0c7d9b
FieldFrom #1232To #2793
mathlib.decl
mathlib.match_kind
mathlib.module
noteNo general compositional-inverse existence theorem for `PowerSeries.subst` is present in Mathlib.
statusnot_formalized
modifiedFormal derivativeb51e149a1020
FieldFrom #1232To #2793
mathlib.declPowerSeries.derivative
mathlib.match_kindexact
mathlib.moduleMathlib.RingTheory.PowerSeries.Derivative
note`PowerSeries.derivative R : Derivation R R⟦X⟧ R⟦X⟧` (notation `d⁄dX`).
statusformalized
modifiedR-linearity of formal derivative2154fe26664d
FieldFrom #1232To #2793
mathlib.declPowerSeries.derivative
mathlib.match_kindinvocation
mathlib.moduleMathlib.RingTheory.PowerSeries.Derivative
notePackaged as a `Derivation`, whose bundled type carries the `R`-linearity axioms `map_add'` and `map_smul'`.
statusformalized
modifiedProduct rule497cf09ebad8
FieldFrom #1232To #2793
mathlib.declPowerSeries.derivativeFun_mul
mathlib.match_kindexact
mathlib.moduleMathlib.RingTheory.PowerSeries.Derivative
noteLabelled 'Leibniz rule for formal power series' in the file; built into the `Derivation` bundle.
statusformalized
modifiedChain rulec5dd38936218
FieldFrom #1232To #2793
mathlib.declPowerSeries.derivative_subst
mathlib.match_kindexact
mathlib.moduleMathlib.RingTheory.PowerSeries.Derivative
note`d⁄dX (f.subst g) = (d⁄dX f).subst g * d⁄dX g` under `HasSubst g`.
statusformalized
modifiedFormal antiderivative4488be2940a4
FieldFrom #1232To #2793
mathlib.decl
mathlib.match_kind
mathlib.module
noteNo `PowerSeries.antiderivative` / formal integral operator exists in Mathlib.
statusnot_formalized
modifiedR-linearity of formal antiderivativecccac219c13b
FieldFrom #1232To #2793
mathlib.decl
mathlib.match_kind
mathlib.module
noteDepends on the missing formal antiderivative.
statusnot_formalized
modifiedAntiderivative is right inverse of derivative5442b5ef3bac
FieldFrom #1232To #2793
mathlib.decl
mathlib.match_kind
mathlib.module
noteDepends on the missing formal antiderivative.
statusnot_formalized
modifiedFormal power series ring contains polynomial ringf3499358128f
FieldFrom #1232To #2793
labelPolynomials as subringFormal power series ring contains polynomial ring
mathlib.declPolynomial.coeToPowerSeries.algHom
mathlib.match_kindexact
mathlib.moduleMathlib.RingTheory.PowerSeries.Basic
noteRelabeled: original 'Polynomials as subring' captured only part of the statement, which also asserts algebra structure.
provenanceai-agent1ai-moderated
statusformalized
modifiedJacobson radicalf281dbbdd218
FieldFrom #1232To #2793
mathlib.decl
mathlib.match_kind
mathlib.module
noteNo lemma computing `Ring.jacobson R⟦X⟧` (or its containment) is present in the PowerSeries files.
statusnot_formalized
modifiedMaximal ideals characterization88a0c95faae7
FieldFrom #1232To #2793
mathlib.declPowerSeries.maximalIdeal_eq_span_X
mathlib.match_kindspecial_case
mathlib.moduleMathlib.RingTheory.PowerSeries.Inverse
noteThe unique maximal ideal of `k⟦X⟧` (k a field) is `(X)`; the correspondence with maximal ideals of general `R` is not stated.
statuspartial
modifiedAlgebraic properties inherited (local, Noetherian, etc.)2ccac1137e8b
FieldFrom #1232To #2793
mathlib.declPowerSeries.instIsNoetherianRing
mathlib.match_kindinvocation
mathlib.moduleMathlib.RingTheory.PowerSeries.Ideal
note`IsNoetherianRing R⟦X⟧` for Noetherian R (`PowerSeries.Ideal`); `IsLocalRing` inheritance is in `MvPowerSeries.Inverse`.
statusformalized
modifiedCompleteness of formal power series metricb956cf22730c
FieldFrom #1232To #2793
mathlib.declPowerSeries.WithPiTopology.instCompleteSpace
mathlib.match_kindgeneralization
mathlib.moduleMathlib.RingTheory.PowerSeries.PiTopology
noteCompleteness is proved for the pi-uniform structure; there is no metric-space version because no metric is defined.
statuspartial
modifiedCompactness iff R finitee0c1884e20f8
FieldFrom #1232To #2793
mathlib.decl
mathlib.match_kind
mathlib.module
noteNo `CompactSpace (PowerSeries R) ↔ Finite R` lemma found in the PowerSeries files.
statusnot_formalized
modifiedWeierstrass preparation theoremaef63a3f5f1c
FieldFrom #1232To #2793
mathlib.declPowerSeries.exists_isWeierstrassFactorization
mathlib.match_kindexact
mathlib.moduleMathlib.RingTheory.PowerSeries.WeierstrassPreparation
noteFor a complete local ring, any power series whose image in the residue field is nonzero factors as (distinguished polynomial)·(unit).
statusformalized
modifiedInterpreting formal power series as functions78e06f82fda8
FieldFrom #1232To #2793
mathlib.declPowerSeries.aeval
mathlib.match_kindexact
mathlib.moduleMathlib.RingTheory.PowerSeries.Evaluation
note`PowerSeries.aeval ha : R⟦X⟧ →ₐ[R] S` evaluates a power series at a topologically nilpotent element.
statusformalized
modifiedExplicit multiplicative inverse formula8bba482a4766
FieldFrom #1232To #2793
mathlib.declPowerSeries.coeff_invOfUnit
mathlib.match_kindexact
mathlib.moduleMathlib.RingTheory.PowerSeries.Inverse
noteRecursive coefficient formula for `invOfUnit`.
statusformalized
modifiedFormal Laurent series0c12ddfa97ad
FieldFrom #1232To #2793
mathlib.declLaurentSeries
mathlib.match_kindexact
mathlib.moduleMathlib.RingTheory.LaurentSeries
note`LaurentSeries R := HahnSeries ℤ R`, notation `R⸨X⸩`.
statusformalized
modifiedOrder of a formal Laurent seriesabafe7312d4a
FieldFrom #1232To #2793
mathlib.declHahnSeries.order
mathlib.match_kindgeneralization
mathlib.moduleMathlib.RingTheory.HahnSeries.Basic
note`HahnSeries.order` / `orderTop` specializes to `LaurentSeries` since it is `HahnSeries ℤ`.
statusformalized
modifiedLaurent series of order -38a098d77cffd
FieldFrom #1232To #2793
mathlib.decl
mathlib.match_kind
mathlib.module
noteIllustrative example, not a named lemma.
statusnot_formalized
modifiedMultiplication of formal Laurent series156200864476
FieldFrom #1232To #2793
mathlib.declHahnSeries.instMul
mathlib.match_kindgeneralization
mathlib.moduleMathlib.RingTheory.HahnSeries.Multiplication
noteMultiplication is inherited from the `HahnSeries` (semi)ring structure.
statusformalized
modifiedRing of formal Laurent series as localization886ad66ca522
FieldFrom #1232To #2793
mathlib.declLaurentSeries.of_powerSeries_localization
mathlib.match_kindexact
mathlib.moduleMathlib.RingTheory.LaurentSeries
note`IsLocalization (Submonoid.powers X) R⸨X⸩` witnesses `R⸨X⸩ = R⟦X⟧[X⁻¹]`.
statusformalized
modifiedFormal derivative of Laurent series8dac3822f501
FieldFrom #1232To #2793
mathlib.declLaurentSeries.derivative
mathlib.match_kindexact
mathlib.moduleMathlib.RingTheory.LaurentSeries
note`LaurentSeries.derivative = hasseDeriv 1`; a general `hasseDeriv k` operator is also defined.
statusformalized
modifiedFormal residue7acd7dccf3f5
FieldFrom #1232To #2793
mathlib.decl
mathlib.match_kind
mathlib.module
noteNo `LaurentSeries.residue` (coefficient at X⁻¹ as a K-derivation) in Mathlib.
statusnot_formalized
modifiedResidue map exact sequencece9f6d255f13
FieldFrom #1232To #2793
mathlib.decl
mathlib.match_kind
mathlib.module
noteDepends on the missing formal residue.
statusnot_formalized
modifiedRules of calculus for formal residue41d264aa75cc
FieldFrom #1232To #2793
mathlib.decl
mathlib.match_kind
mathlib.module
noteDepends on the missing formal residue.
statusnot_formalized
modifiedLagrange inversion formula7e768e3434b8
FieldFrom #1232To #2793
mathlib.decl
mathlib.match_kind
mathlib.module
noteNo Lagrange inversion formula for formal power series in Mathlib.
statusnot_formalized
modifiedGeneralization of Lagrange inversiona81efebea88d
FieldFrom #1232To #2793
mathlib.decl
mathlib.match_kind
mathlib.module
noteThe basic Lagrange inversion theorem is not yet in Mathlib.
statusnot_formalized
modifiedFormal power series in several variables0ed52806cf28
FieldFrom #1232To #2793
mathlib.declMvPowerSeries
mathlib.match_kindexact
mathlib.moduleMathlib.RingTheory.MvPowerSeries.Basic
note`MvPowerSeries σ R := (σ →₀ ℕ) → R`.
statusformalized
modifiedTopology on series in several variables3b7507cd5a1d
FieldFrom #1232To #2793
mathlib.declMvPowerSeries.WithPiTopology
mathlib.match_kindexact
mathlib.moduleMathlib.RingTheory.MvPowerSeries.PiTopology
noteProduct/pi topology on `MvPowerSeries σ R`.
statusformalized
modifiedInvertibility in several variables48d8fc0bd75b
FieldFrom #1232To #2793
mathlib.declMvPowerSeries.isUnit_iff_constantCoeff
mathlib.match_kindexact
mathlib.moduleMathlib.RingTheory.MvPowerSeries.Inverse
note`IsUnit φ ↔ IsUnit (constantCoeff φ)` for `MvPowerSeries σ R`.
statusformalized
modifiedComposition in several variables0286af3aa078
FieldFrom #1232To #2793
mathlib.declMvPowerSeries.subst
mathlib.match_kindexact
mathlib.moduleMathlib.RingTheory.MvPowerSeries.Substitution
note`MvPowerSeries.subst a f` under `MvPowerSeries.HasSubst a`.
statusformalized
modifiedPartial derivative operatorsa9c0c5129306
FieldFrom #1232To #2793
mathlib.decl
mathlib.match_kind
mathlib.module
noteNo `MvPowerSeries.pderiv` defined in Mathlib (unlike `MvPolynomial.pderiv`).
statusnot_formalized
modifiedUniversal property (several variables)2ba76c51ae53
FieldFrom #1232To #2793
mathlib.declMvPowerSeries.aeval_unique
mathlib.match_kindexact
mathlib.moduleMathlib.RingTheory.MvPowerSeries.Evaluation
noteA continuous R-algebra hom `MvPowerSeries σ R →ₐ[R] S` is determined by its values on X_s.
statusformalized
modifiedNon-commuting variables / Magnus ringc24f809f388c
FieldFrom #1232To #2793
mathlib.decl
mathlib.match_kind
mathlib.module
noteNo Magnus ring / noncommutative-variable formal power series construction in Mathlib.
statusnot_formalized
modifiedFormal power series over a semiring9f51278e403b
FieldFrom #1232To #2793
mathlib.declMvPowerSeries
mathlib.match_kindexact
mathlib.moduleMathlib.RingTheory.MvPowerSeries.Basic
noteThe Mathlib definition is already given for `[Semiring R]` (and `PowerSeries` inherits).
statusformalized
modifiedSupport and characteristic series4889478db58e
FieldFrom #1232To #2793
mathlib.decl
mathlib.match_kind
mathlib.module
noteNo `PowerSeries.support` or characteristic-series construction; `HahnSeries.support` exists but that is a different object.
statusnot_formalized
modifiedSum, Cauchy product, Hadamard product on a semiringeaf364375a08
FieldFrom #1232To #2793
mathlib.declPowerSeries.coeff_mul
mathlib.match_kindspecial_case
mathlib.moduleMathlib.RingTheory.PowerSeries.Basic
noteAddition and Cauchy product are provided by the (semi)ring instance; no Hadamard-product operator is defined for `PowerSeries`.
statuspartial
modifiedFormal power series on an ordered abelian group4064f0e676e1
FieldFrom #1232To #2793
mathlib.declHahnSeries
mathlib.match_kindexact
mathlib.moduleMathlib.RingTheory.HahnSeries.Basic
note`HahnSeries Γ R` for a partially-ordered Γ with well-founded (isPWO) support.
statusformalized
modifiedHahn series field properties293fe538bc6b
FieldFrom #1232To #2793
mathlib.declHahnSeries.instField
mathlib.match_kindexact
mathlib.moduleMathlib.RingTheory.HahnSeries.Summable
note`HahnSeries Γ R` is a field when Γ is a linearly ordered abelian group and R is a field.
statusformalized
addedUniqueness of multiplicative inversef8a2e3bfed78
addedCauchy product finiteness of each coefficientf2e39f18e746
addedEmbedding of R into R[[X]] and the indeterminate Xe568d9fe41e1
addedEquivalence of product/I-adic/metric topologies61ac90b3a80a
addedRecursive formula for coefficients of the n-th power84e65b36bd57
addedExponent rules for complex powers4a36928c2cdf
addedRecursive formula for coefficients of the inverse series443bbce2906b
addedCoefficient of composition via truncated polynomials1dc8270786d7
addedRecursive computation of composition inverse coefficients9ebbba45aedb
addedTaylor-series representation via formal derivativesbddd01401dc4
addedField of fractions of K[[X]] equals K((X))8a8f80abeb53
addedOrder/derivative relation ord(f') = ord(f) - 1b61e777970e7
addedFormal residue is a K-derivation7e1803ee1f34
addedLagrange inversion n=1 special caseebb68a0f4d1c