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A187646 (Signless) Central Stirling numbers of the first kind s(2n,n). 16
1, 1, 11, 225, 6769, 269325, 13339535, 790943153, 54631129553, 4308105301929, 381922055502195, 37600535086859745, 4070384057007569521, 480544558742733545125, 61445535102359115635655, 8459574446076318147830625 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Number of permutations with n cycles on a set of size 2n.

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..200

FORMULA

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

MAPLE

seq(abs(Stirling1(2*n, n)), n=0..20);

MATHEMATICA

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 *)

PROG

(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

CROSSREFS

Cf. A008275, A007820, A187235, A237993, A242676, A285862.

Sequence in context: A089917 A294388 A281257 * A170948 A245076 A120850

Adjacent sequences:  A187643 A187644 A187645 * A187647 A187648 A187649

KEYWORD

nonn,easy

AUTHOR

Emanuele Munarini, Mar 12 2011

STATUS

approved

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Last modified July 20 23:29 EDT 2019. Contains 325189 sequences. (Running on oeis4.)