A030201 - OEIS

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A030201

Expansion of eta(q^3)*eta(q^21).

0, 1, 0, 0, -1, 0, 0, -1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, -2, 0, 0, 0, 0, 0, -2, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, -1, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,38

COMMENTS

Multiplicative. See A002655 for formula. - Andrew Howroyd, Aug 05 2018

LINKS

Seiichi Manyama, Table of n, a(n) for n = 0..10000

M. Koike, On McKay's conjecture, Nagoya Math. J., 95 (1984), 85-89.

FORMULA

Expansion of x * Product_{k>=1} (1 - x^(3*k)) * (1 - x^(21*k)). - Seiichi Manyama, Oct 18 2016

a(3*n + 1) = A002655(n), a(3*n) = a(3*n + 2) = 0. - Andrew Howroyd, Aug 05 2018

MATHEMATICA

q QPochhammer[q^3] QPochhammer[q^21] + O[q]^105 // CoefficientList[#, q]& (* Jean-François Alcover, Sep 06 2019 *)

PROG

(PARI) seq(n)={concat([0], Vec(eta(x^3 + O(x*x^n)) * eta(x^21 + O(x*x^n))))} \\ Andrew Howroyd, Aug 05 2018

CROSSREFS

Expansion of eta(q^k)*eta(q^(24 - k)): A030199 (k=1), this sequence (k=3), A030213 (k=5), A030214 (k=7), A030215 (k=9), A030216 (k=10), A030217 (k=11).

Cf. A002655.

Sequence in context: A070536 A318886 A369873 * A349797 A055668 A045839

Adjacent sequences: A030198 A030199 A030200 * A030202 A030203 A030204

KEYWORD

sign,mult

AUTHOR

N. J. A. Sloane

STATUS

approved