A258941 Convolution inverse of A058537.

1, -7, 41, -253, 1555, -9532, 58463, -358600, 2199546, -13491360, 82752059, -507576937, 3113328401, -19096245457, 117130782240, -718445946527, 4406737223117, -27029636742811, 165791883077354, -1016918901125280, 6237482995373629, -38258895644996020

Offset

0,2

Comments

Cubic AGM theta functions: a(q) (see A004016), b(q) (A005928), c(q) (A005882).

Convolution square is A328785. - Michael Somos, Nov 02 2019

Links

Vaclav Kotesovec, Table of n, a(n) for n = 0..1260

Formula

a(n) ~ (-1)^n * c * exp(Pi*n/sqrt(3)), where c = A258942 = 8*exp(Pi/(6*sqrt(3))) * Pi^(5/2) / Gamma(1/6)^3 = 1.09786330972731096865822482325074133091288... . - Vaclav Kotesovec, Nov 14 2015

Expansion of q^(-1/6)* eta[q]*eta[q^9]^2/(eta[q]^3 + 9*eta[q^9]^3) in powers of q. - G. C. Greubel, Jun 22 2018

Expansion of q^(-1/6) * 3^(-1/2) * sqrt(b(q)*c(q))/a(q) in powers of q where a(), b(), c() are cubic AGM functions. - Michael Somos, Nov 02 2019

Example

G.f. = 1 - 7*x + 41*x^2 - 253*x^3 + 1555*x^4 - 9532*x^5 + ... - Michael Somos, Nov 02 2019
G.f. = q - 7*q^7 + 41*q^13 - 253*q^19 + 1555*q^25 - 9532*q^31 + ... - Michael Somos, Nov 02 2019

Mathematica

CoefficientList[Series[QPochhammer[x, x] * QPochhammer[x^3, x^3]^2 / (QPochhammer[x, x]^3 + 9*x*QPochhammer[x^9, x^9]^3), {x, 0, 50}], x]
eta[q_]:= q^(1/24)*QPochhammer[q]; CoefficientList[Series[q^(-1/6)* eta[q]*eta[q^9]^2/(eta[q]^3 + 9*eta[q^9]^3), {q, 0, 60}], q] (* G. C. Greubel, Jun 22 2018 *)
a[ n_] := SeriesCoefficient[ QPochhammer[x] QPochhammer[x^3]^2 / (QPochhammer[x]^3 + 9 x QPochhammer[x^9]^3), {x, 0, n}]; (* Michael Somos, Nov 02 2019 *)

Prog

(PARI) q='q+O('q^50); A = eta(q)*eta(q^3)^2/(eta(q)^3 + 9*q*eta(q^9)^3); Vec(A) \\ G. C. Greubel, Jun 22 2018

Crossrefs

Cf. A058537, A051273, A058092, A115784, A258942, A328785.

Sequence in context: A108983 A115137 A036730 * A080047 A297671 A356298

Adjacent sequences: A258938 A258939 A258940 * A258942 A258943 A258944

Keyword

sign

Author

Vaclav Kotesovec, Nov 07 2015

Status

approved