OFFSET
0,6
MATHEMATICA
nmax = 54; CoefficientList[Series[Sum[x^(k (k + 1)/2) Product[(1 + x^j)^j, {j, 1, k}], {k, 0, nmax}], {x, 0, nmax}], x]
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Mar 06 2019
STATUS
approved