OFFSET
0,29
LINKS
Ilya Gutkovskiy, Scatterplot of a(n) up to n=10000
MATHEMATICA
nmax = 85; CoefficientList[Series[Product[(1 - x^(4 k - 3)) (1 - x^(4 k)), {k, 1, nmax}], {x, 0, nmax}], x]
a[0] = 1; a[n_] := a[n] = -(1/n) Sum[DivisorSum[k, # &, Or[Mod[#, 4] == 0, Mod[#, 4] == 1] &] a[n - k], {k, 1, n}]; Table[a[n], {n, 0, 85}]
CROSSREFS
KEYWORD
sign
AUTHOR
Ilya Gutkovskiy, Jun 27 2024
STATUS
approved