[go: up one dir, main page]

login
A088336
Number of permutations in the symmetric group S_n that have even number of transpositions in their cycle decomposition.
6
1, 1, 1, 3, 18, 90, 480, 3360, 27720, 249480, 2479680, 27276480, 327650400, 4259455200, 59623724160, 894355862400, 14309953257600, 243269205379200, 4378836875212800, 83197900629043200, 1663958347802150400, 34943125303845158400, 768748742605299456000
OFFSET
0,4
LINKS
FORMULA
E.g.f.: (exp(-x^2)+1)/(1-x)/2. - Vladeta Jovovic, Nov 09 2003
a(n) ~ n! * (1+exp(-1))/2. - Vaclav Kotesovec, Oct 08 2013
MATHEMATICA
mx = 21; Rest[ Range[0, mx]! CoefficientList[ Series[(Exp[-x^2] + 1)/(1 - x)/2, {x, 0, mx}], x]] (* Robert G. Wilson v, May 04 2013 *)
PROG
(PARI) x='x+O('x^50); Vec(serlaplace((exp(-x^2)+1)/(1-x)/2)) \\ G. C. Greubel, Aug 20 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Yuval Dekel (dekelyuval(AT)hotmail.com), Nov 07 2003
EXTENSIONS
More terms from Robert G. Wilson v, May 04 2013
a(0) = 1 prepended by Alois P. Heinz, Jun 14 2015
STATUS
approved