OFFSET
0,20
FORMULA
G.f.: Sum_{k>=1} k! * x^(k*(k + 17)/2) / Product_{j=1..k-1} (1 - x^j).
EXAMPLE
a(30) = 8 because we have [21, 9], [11, 10, 9], [11, 9, 10], [10, 11, 9], [10, 9, 11], [9, 21], [9, 11, 10] and [9, 10, 11].
MATHEMATICA
nmax = 67; CoefficientList[Series[Sum[k! x^(k (k + 17)/2)/Product[1 - x^j, {j, 1, k - 1}], {k, 1, nmax}], {x, 0, nmax}], x]
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Nov 25 2020
STATUS
approved