OFFSET
0,5
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..10000 (terms 0..1000 from G. C. Greubel)
Vaclav Kotesovec, A method of finding the asymptotics of q-series based on the convolution of generating functions, arXiv:1509.08708 [math.CO], 2015-2016.
J. Mc Laughlin, A. V. Sills and P. Zimmer, Rogers-Ramanujan-Slater Type Identities, Electronic J. Combinatorics, DS15, 1-59, May 31, 2008. See "2.7 The Rogers-Selberg Mod 7 Identities".
Eric Weisstein's World of Mathematics, Rogers-Selberg Identities
FORMULA
Expansion of f(-q, -q^6) / f(-q^2) in powers of q where f() is Ramanujan's theta function.
Euler transform of period 14 sequence [ -1, 1, 0, 1, 0, 0, -1, 0, 0, 1, 0, 1, -1, 0, ...]. - Michael Somos, Dec 04 2007
a(n) ~ (-1)^n * cos(Pi/14) * 11^(1/4) * exp(Pi*sqrt(11*n/42)) / (3^(1/4) * 14^(3/4) * n^(3/4)). - Vaclav Kotesovec, Oct 04 2015
EXAMPLE
1 - q + q^2 - q^3 + 2*q^4 - 2*q^5 + 2*q^6 - 3*q^7 + 4*q^8 - 4*q^9 + 5*q^10 + ...
MATHEMATICA
nmax=60; CoefficientList[Series[Product[(1-x^(7*k-1))*(1-x^(7*k-6))*(1-x^(7*k))/(1-x^(2*k)), {k, 1, nmax}], {x, 0, nmax}], x] (* Vaclav Kotesovec, Oct 04 2015 *)
PROG
(PARI) {a(n) = if( n<0, 0, polcoeff( prod(k=1, n, (1 - x^k + x*O(x^n))^[0, 1, -1, 0, -1, 0, 0, 1, 0, 0, -1, 0, -1, 1][k%14+1]), n))} /* Michael Somos, Dec 04 2007 */
CROSSREFS
KEYWORD
sign
AUTHOR
Eric W. Weisstein, Mar 06 2005
STATUS
approved