OFFSET
1,1
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..424
FORMULA
a(n) ~ -(-1)^n * exp(Pi*sqrt(3)*n) / (8*n). - Vaclav Kotesovec, Jun 03 2018
MATHEMATICA
terms = 13;
E2[x_] = 1 - 24*Sum[k*x^k/(1 - x^k), {k, 1, terms}];
E4[x_] = 1 + 240*Sum[k^3*x^k/(1 - x^k), {k, 1, terms}];
E6[x_] = 1 - 504*Sum[k^5*x^k/(1 - x^k), {k, 1, terms}];
a[n_] := (1/(24 n))*Sum[MoebiusMu[n/d]*SeriesCoefficient[E4[x]/E2[x] - E6[x]/E4[x], {x, 0, d}], {d, Divisors[n]}];
Array[a, terms] (* Jean-François Alcover, Feb 26 2018 *)
CROSSREFS
KEYWORD
sign
AUTHOR
Seiichi Manyama, Feb 12 2018
STATUS
approved