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A244035
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a(n) = Sum_{d|n} Sum{t|d} moebius(d/t)*binomial(3*t,t)/(3*d^2).
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0
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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
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OFFSET
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1,2
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LINKS
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MAPLE
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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)];
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MATHEMATICA
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a[n_] := Sum[MoebiusMu[d/t]*Binomial[3*t, t]/(3*d^2), {d, Divisors[n]}, {t, Divisors[d]}];
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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