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A244035 a(n) = Sum_{d|n} Sum{t|d} moebius(d/t)*binomial(3*t,t)/(3*d^2). 0
1, 2, 4, 12, 41, 176, 792, 3840, 19291, 100182, 533160, 2897544, 16020564, 89898944, 510914744, 2936004072, 17036988567, 99718480238, 588166176660, 3493203829992, 20876368407633, 125470501764720, 757994313694512, 4600845871441080, 28047225141946116, 171662437354159416 (list; graph; refs; listen; history; text; internal format)
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 (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-Fran├žois Alcover, Dec 05 2017 *)

CROSSREFS

Sequence in context: A222919 A264760 A090959 * A126942 A126947 A188494

Adjacent sequences:  A244032 A244033 A244034 * A244036 A244037 A244038

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Jun 28 2014

STATUS

approved

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Last modified November 12 07:03 EST 2019. Contains 329052 sequences. (Running on oeis4.)