OFFSET
0,9
FORMULA
G.f.: Sum_{k>=0} x^(3*k)/Product_{j=1..k} (1 - j * x^2).
PROG
(PARI) a(n) = sum(k=0, n\2, stirling(k, n-2*k, 2));
(PARI) my(N=40, x='x+O('x^N)); Vec(sum(k=0, N, x^(3*k)/prod(j=1, k, 1-j*x^2)))
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Oct 21 2022
STATUS
approved