OFFSET
0,3
COMMENTS
Compare to g.f. of partitions in which no parts are multiples of 4:
g.f. of A001935 = exp( Integral (theta_3(x)^4-1)/(8x) dx ).
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..10000
FORMULA
a(n) ~ exp(2*Pi*n^(3/4)/3 - Zeta(3)/Pi^2) / (4*n^(5/8)). - Vaclav Kotesovec, Apr 10 2019
EXAMPLE
G.f.: A(x) = 1 + x + 4*x^2 + 13*x^3 + 35*x^4 + 87*x^5 +...
log(A(x)) = x + 7*x^2/2 + 28*x^3/3 + 71*x^4/4 + 126*x^5/5 +...+ A008457(n)*x^n/n +...
MATHEMATICA
nmax = 40; Abs[CoefficientList[Series[Product[1/(1 - x^k)^((-1)^k*k^2), {k, 1, nmax}], {x, 0, nmax}], x]] (* Vaclav Kotesovec, Apr 10 2019 *)
nmax = 40; CoefficientList[Series[Product[(1 + x^(2*k - 1))^((2*k - 1)^2)/(1 - x^(2*k))^(4*k^2), {k, 1, nmax}], {x, 0, nmax}], x] (* Vaclav Kotesovec, Apr 10 2019 *)
PROG
(PARI) {a(n)=polcoeff(exp(sum(m=1, n, sumdiv(m, d, (-1)^(m-d)*d^3)*x^m/m)+x*O(x^n)), n)}
(PARI) {a(n)=local(theta3=1+sum(m=1, sqrtint(2*n+2), 2*x^(m^2)+x*O(x^n))); polcoeff(exp(intformal((theta3^8-1)/(16*x))), n)}
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, May 03 2010, May 08 2010
STATUS
approved