OFFSET
0,9
FORMULA
G.f.: Sum_{k>=0} x^(3*k*(3*k+1)/2) / Product_{j=1..3*k} (1-x^j) = Sum_{k>=0} Product_{j=1..3*k} (x^j/(1-x^j)).
EXAMPLE
a(12) = 7 counts these partitions: 921, 831, 741, 732, 651, 642, 543.
PROG
(PARI) my(N=70, x='x+O('x^N)); Vec(sum(k=0, N, prod(j=1, 3*k, x^j/(1-x^j))))
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, May 23 2024
STATUS
approved