OFFSET
0,8
LINKS
Eric Weisstein's World of Mathematics, Hexagonal Pyramidal Number
FORMULA
G.f.: 1/(1 - Sum_{k>=1} x^(k*(k+1)*(4*k-1)/6)).
MATHEMATICA
nmax = 53; CoefficientList[Series[1/(1 - Sum[x^(k (k + 1) (4 k - 1)/6), {k, 1, nmax}]), {x, 0, nmax}], x]
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Dec 29 2018
STATUS
approved