A244036 - OEIS

A244036

a(n) = Sum_{d|n} Sum{t|d} (n/d)*moebius(d/t)*binomial(3*t,t)/(3*d^2).

1, 3, 6, 16, 45, 186, 798, 3860, 19305, 100235, 533170, 2897760, 16020576, 89899754, 510914850, 2936007952, 17036988583, 99718499907, 588166176678, 3493203930320, 20876368409253, 125470502297910, 757994313694534, 4600845874346712, 28047225141946300, 171662437370180016

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OFFSET

1,2

LINKS

Table of n, a(n) for n=1..26.

M. Isachenkov, I. Kirsch, V. Schomerus, Chiral Primaries in Strange Metals, arXiv preprint arXiv:1403.6857 [hep-th], 2014. See display following (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 + (N/Na)*mobius(Na/n)*binomial(3*n, n)/(3*Na^2); od: od:

ans;

end;

[seq(f(n), n=1..30)];

MATHEMATICA

a[n_] := Sum[(n/d) MoebiusMu[d/t] Binomial[3t, t]/(3d^2), {d, Divisors[n]}, {t, Divisors[d]}];

Array[a, 26] (* Jean-François Alcover, Dec 06 2017, from Maple *)

CROSSREFS

Sequence in context: A086811 A106361 A113040 * A220184 A007002 A305136

Adjacent sequences: A244033 A244034 A244035 * A244037 A244038 A244039

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Jun 28 2014

STATUS

approved