OFFSET
0,82
COMMENTS
Number of partitions of n into distinct heptagonal numbers (A000566).
LINKS
Eric Weisstein's World of Mathematics, Heptagonal Number
FORMULA
G.f.: Product_{k>=1} (1 + x^(k*(5*k-3)/2)).
EXAMPLE
a(81) = 2 because we have [81] and [55, 18, 7, 1].
MATHEMATICA
nmax = 120; CoefficientList[Series[Product[1 + x^(k (5 k - 3)/2), {k, 1, nmax}], {x, 0, nmax}], x]
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Dec 09 2016
STATUS
approved