OFFSET
3,4
FORMULA
G.f.: ( Sum_{k>=1} x^binomial(k+2,3) )^3.
MATHEMATICA
nmax = 95; CoefficientList[Series[Sum[x^Binomial[k + 2, 3], {k, 1, nmax}]^3, {x, 0, nmax}], x] // Drop[#, 3] &
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Feb 19 2021
STATUS
approved