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A187646
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(Signless) Central Stirling numbers of the first kind s(2n,n).
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19
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1, 1, 11, 225, 6769, 269325, 13339535, 790943153, 54631129553, 4308105301929, 381922055502195, 37600535086859745, 4070384057007569521, 480544558742733545125, 61445535102359115635655, 8459574446076318147830625, 1247677142707273537964543265, 196258640868140652967646352465
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OFFSET
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0,3
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COMMENTS
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Number of permutations with n cycles on a set of size 2n.
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LINKS
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FORMULA
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Asymptotic: a(n) ~ (2*n/(e*z*(1-z)))^n*sqrt((1-z)/(2*Pi*n*(2z-1))), where z=0.715331862959... is a root of the equation z = 2*(z-1)*log(1-z). - Vaclav Kotesovec, May 30 2011
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MAPLE
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seq(abs(Stirling1(2*n, n)), n=0..20);
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MATHEMATICA
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Table[Abs[StirlingS1[2n, n]], {n, 0, 12}]
N[1 + 1/(2 LambertW[-1, -Exp[-1/2]/2]), 50] (* The constant z in the asymptotic - Vladimir Reshetnikov, Oct 08 2016 *)
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PROG
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(Maxima) makelist(abs(stirling1(2*n, n)), n, 0, 12);
(PARI) for(n=0, 50, print1(abs(stirling(2*n, n, 1)), ", ")) \\ G. C. Greubel, Nov 09 2017
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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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