A261394 Expansion of phi(q)^4 / phi(q^3) in powers of q where phi() is a Ramanujan theta function.

1, 8, 24, 30, 8, 0, 36, 48, 24, 32, 48, 48, 30, 0, 48, 72, 8, 48, 96, 48, 0, 0, 96, 96, 36, 56, 48, 102, 48, 0, 120, 48, 24, 72, 48, 96, 32, 0, 96, 120, 48, 48, 144, 144, 48, 0, 96, 96, 30, 56, 120, 144, 0, 0, 108, 96, 48, 120, 144, 48, 72, 0, 144, 192, 8, 96

Offset

0,2

Comments

Ramanujan theta functions: f(q) (see A121373), phi(q) (A000122), psi(q) (A010054), chi(q) (A000700).

Links

G. C. Greubel, Table of n, a(n) for n = 0..2500

Michael Somos, Introduction to Ramanujan theta functions

Eric Weisstein's World of Mathematics, Ramanujan Theta Functions

Formula

Euler transform of period 12 sequence [ 8, -12, 6, -4, 8, -9, 8, -4, 6, -12, 8, -3, ...].

a(n) = A004013(12*n).

Example

G.f. = 1 + 8*x + 24*x^2 + 30*x^3 + 8*x^4 + 36*x^6 + 48*x^7 + 24*x^8 + ...

Mathematica

a[ n_] := SeriesCoefficient[ EllipticTheta[ 3, 0, q]^4 / EllipticTheta[ 3, 0, q^3], {q, 0, n}];

Prog

(PARI) {a(n) = my(A); if( n<0, 0, A = x * O(x^n); polcoeff( eta(x^2 + A)^20 * eta(x^3 + A)^2 * eta(x^12 + A)^2 / (eta(x + A)^8 * eta(x^4 + A)^8 * eta(x^6 + A)^5), n))};

Crossrefs

Cf. A004013.

Sequence in context: A212861 A333961 A038524 * A162829 A303796 A175368

Adjacent sequences: A261391 A261392 A261393 * A261395 A261396 A261397

Keyword

nonn

Author

Michael Somos, Aug 17 2015

Status

approved