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A333817
G.f.: Sum_{k>=1} x^(k*(5*k - 3)/2) / (1 - x^(5*k)).
5
1, 0, 0, 0, 0, 1, 1, 0, 0, 0, 1, 0, 0, 0, 0, 1, 1, 1, 0, 0, 1, 0, 0, 0, 0, 1, 1, 0, 0, 0, 1, 0, 1, 1, 0, 1, 1, 0, 0, 0, 1, 0, 0, 0, 0, 1, 1, 1, 0, 0, 1, 0, 0, 1, 1, 1, 1, 0, 0, 0, 1, 0, 1, 0, 0, 1, 1, 0, 0, 0, 1, 0, 0, 1, 0, 1, 1, 1, 0, 1, 2, 0, 0, 0, 0, 1, 1, 0, 0, 0, 1, 0, 1
OFFSET
1,81
COMMENTS
Number of ways to write n as the difference of two heptagonal numbers.
FORMULA
G.f.: Sum_{i>=0} Sum_{j>=i} Product_{k=i..j} x^(5*k + 1).
MATHEMATICA
nmax = 93; CoefficientList[Series[Sum[x^(k (5 k - 3)/2)/(1 - x^(5 k)), {k, 1, nmax}], {x, 0, nmax}], x] // Rest
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Apr 06 2020
STATUS
approved