OFFSET
1,2
LINKS
M. Isachenkov, I. Kirsch, V. Schomerus, Chiral Primaries in Strange Metals, arXiv preprint arXiv:1403.6857 [hep-th], 2014. See (3.5).
MAPLE
with(numtheory);
f:=proc(N) local Na, n, ans;
ans:=0;
for Na in divisors(N) do
for n in divisors(Na) do
ans := ans + mobius(Na/n)*binomial(3*n, n)/(3*Na^2); od: od:
ans;
end;
[seq(f(n), n=1..30)];
MATHEMATICA
a[n_] := Sum[MoebiusMu[d/t]*Binomial[3*t, t]/(3*d^2), {d, Divisors[n]}, {t, Divisors[d]}];
Array[a, 26] (* Jean-François Alcover, Dec 05 2017 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Jun 28 2014
STATUS
approved