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A120844
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Number of multi-trace BPS operators for the quiver gauge theory of the orbifold C^2/Z_2.
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6
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1, 3, 11, 32, 90, 231, 576, 1363, 3141, 7003, 15261, 32468, 67788, 138892, 280103, 556302, 1089991, 2108332, 4030649, 7620671, 14261450, 26431346, 48544170, 88393064, 159654022, 286149924, 509137464, 899603036, 1579014769
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OFFSET
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0,2
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LINKS
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FORMULA
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G.f.: exp(sum_{n>0} (3 x^n - x^{2n} ) / n (1-x^n)^2.
a(n) ~ Zeta(3)^(7/18) * exp(1/6 - Pi^4/(864*Zeta(3)) + Pi^2 * n^(1/3)/(3 * 2^(5/3) * Zeta(3)^(1/3)) + 3 * (Zeta(3)/2)^(1/3) * n^(2/3)) / (A^2 * 2^(2/9) * 3^(1/2) * Pi * n^(8/9)), where A = A074962 = 1.2824271291... is the Glaisher-Kinkelin constant and Zeta(3) = A002117 = 1.202056903... . - Vaclav Kotesovec, Mar 07 2015
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MAPLE
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with(numtheory): etr:= proc(p) local b; b:=proc(n) option remember; local d, j; if n=0 then 1 else add(add(d*p(d), d=divisors(j)) *b(n-j), j=1..n)/n fi end end: a:=etr(n-> 2*n+1): seq(a(n), n=0..50); # Vaclav Kotesovec, Mar 06 2015 after Alois P. Heinz
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MATHEMATICA
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nmax=50; CoefficientList[Series[Product[1/(1-x^k)^(2*k+1), {k, 1, nmax}], {x, 0, nmax}], x] (* Vaclav Kotesovec, Feb 27 2015 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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Amihay Hanany (hanany(AT)mit.edu), Aug 25 2006
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STATUS
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approved
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