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A316143
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Expansion of e.g.f. Product_{k>=1} 1 / (1 - (exp(x)-1)^k)^2.
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3
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1, 2, 12, 92, 912, 10772, 148512, 2328692, 40842912, 791302772, 16767551712, 385382491892, 9542377300512, 253105962752372, 7156766466076512, 214814484529608692, 6819311473596695712, 228212485803422931572, 8028037725386962194912, 296094910181041530831092
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OFFSET
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0,2
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COMMENTS
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Conjecture: Let k be a positive integer. The sequence obtained by reducing a(n) modulo k is eventually periodic with the period dividing phi(k) = A000010(k). For example, modulo 7 we obtain the sequence [1, 2, 5, 1, 2, 6, 0, 2, 5, 1, 2, 6, 0, 2, 5, 1, 2, 6, 0, ...], with a preperiod of length 1 and an apparent period thereafter of 6 = phi(7). - Peter Bala, Mar 03 2023
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LINKS
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FORMULA
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a(n) ~ n! * exp(Pi * sqrt(2*n/(3*log(2))) - Pi^2 * (1 - 1/log(2)) / 12) / (2^(7/4) * 3^(3/4) * n^(5/4) * (log(2))^(n - 1/4)).
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MATHEMATICA
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nmax = 20; CoefficientList[Series[Product[1/(1-(Exp[x]-1)^k)^2, {k, 1, nmax}], {x, 0, nmax}], x] * Range[0, nmax]!
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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