A193826 Expansion of psi(x^2) * phi(x^7) / (f(-x) * f(-x^7)) in powers of x where phi(), psi(), f() are Ramanujan theta functions.

1, 1, 3, 4, 7, 10, 17, 26, 38, 57, 81, 114, 161, 224, 309, 419, 569, 759, 1011, 1336, 1757, 2296, 2981, 3855, 4956, 6344, 8087, 10272, 12994, 16367, 20561, 25723, 32086, 39902, 49484, 61182, 75439, 92791, 113821, 139294, 170073, 207187, 251853

Offset

0,3

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..1000

Michael Somos, Introduction to Ramanujan theta functions

Eric Weisstein's World of Mathematics, Ramanujan Theta Functions

Formula

Expansion of chi(-x^14)^2 / (chi(-x) * chi(-x^2)^4 * chi(-x^7)^3 ) in powers of x where chi() is a Ramanujan theta function.

Expansion of q^(1/12) * eta(q^4)^2 * eta(q^14)^5 / (eta(q) * eta(q^2) * eta(q^7)^3* eta(q^28)^2) in powers of q.

Euler transform of period 28 sequence [ 1, 2, 1, 0, 1, 2, 4, 0, 1, 2, 1, 0, 1, 0, 1, 0, 1, 2, 1, 0, 4, 2, 1, 0, 1, 2, 1, 0, ...].

a(n) = A102314(4*n).

a(n) ~ exp(4*Pi*sqrt(n/21)) / (2^(5/2) * 21^(1/4) * n^(3/4)). - Vaclav Kotesovec, Nov 15 2017

Example

G.f. = 1 + x + 3*x^2 + 4*x^3 + 7*x^4 + 10*x^5 + 17*x^6 + 26*x^7 + 38*x^8 + ...
G.f. = 1/q + q^11 + 3*q^23 + 4*q^35 + 7*q^47 + 10*q^59 + 17*q^71 + 26*q^83 + ...

Mathematica

a[ n_] := SeriesCoefficient[ QPochhammer[ x, x^2] QPochhammer[ x^7, x^14], {x, 0, 4 n}];
a[ n_] := SeriesCoefficient[ EllipticTheta[ 3, 0, x^7] EllipticTheta[ 2, 0, x] / (2 x^(1/4) QPochhammer[ x] QPochhammer[ x^7]), {x, 0, n}];
a[ n_] := SeriesCoefficient[ QPochhammer[ x^14, x^28]^2 / (QPochhammer[ x, x^2] QPochhammer[ x^2, x^4]^2 QPochhammer[ x^7, x^14]^3), {x, 0, n}];

Prog

(PARI) {a(n) = my(A); if( n<0, 0, A = x * O(x^n); polcoeff( eta(x^4 + A)^2 * eta(x^14 + A)^5 / (eta(x + A) * eta(x^2 + A) * eta(x^7 + A)^3* eta(x^28 + A)^2), n))};

Crossrefs

Cf. A102314.

Sequence in context: A261037 A280423 A143607 * A032715 A293276 A291609

Adjacent sequences: A193823 A193824 A193825 * A193827 A193828 A193829

Keyword

nonn

Author

Michael Somos, Aug 06 2011

Status

approved