OFFSET
0,6
LINKS
Eric Weisstein's World of Mathematics, Square Pyramidal Number
FORMULA
a(n) = [x^n] (Sum_{k>=0} x^(k*(k+1)*(2*k+1)/6))^n.
a(n) = A290430(n,n).
MATHEMATICA
Table[SeriesCoefficient[Sum[x^(k (k + 1) (2 k + 1)/6), {k, 0, n}]^n, {x, 0, n}], {n, 0, 32}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Apr 19 2018
STATUS
approved