A364205 Expansion of Sum_{k>=0} x^(3*k+2) / (1 + x^(3*k+2)).
0, 1, 0, -1, 1, 1, 0, 0, 0, 0, 1, -1, 0, 2, 1, -2, 1, 1, 0, -1, 0, 0, 1, 0, 1, 2, 0, -2, 1, 0, 0, -1, 1, 0, 2, -1, 0, 2, 0, -2, 1, 2, 0, -1, 1, 0, 1, -2, 0, 1, 1, -2, 1, 1, 2, 0, 0, 0, 1, -1, 0, 2, 0, -3, 2, 0, 0, -1, 1, 0, 1, 0, 0, 2, 1, -2, 2, 2, 0, -3, 0, 0, 1, -2, 2, 2, 1, -2, 1, 0, 0, -1
Offset: 1
Keywords
Links
- Seiichi Manyama, Table of n, a(n) for n = 1..10000
Programs
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Mathematica
nmax = 92; CoefficientList[Series[Sum[x^(3 k + 2)/(1 + x^(3 k + 2)), {k, 0, nmax}], {x, 0, nmax}], x] // Rest Table[DivisorSum[n, (-1)^(# + 1) &, MemberQ[{2}, Mod[n/#, 3]] &], {n, 1, 92}]
Formula
a(n) = Sum_{d|n, n/d==2 (mod 3)} (-1)^(d+1).