OFFSET
1,3
LINKS
Vaclav Kotesovec, Table of n, a(n) for n = 1..380
FORMULA
a(n) = n!*Sum_{k=1..n-1} (n^(k-1)*(-1)^(n-2*k-1)*Stirling1(n-k-1, k))/(n-k-1)!, n > 1, a(1)=1.
a(n) ~ n^(n-1) / (sqrt(1-(2-s)*(1-s)*s) * exp(n) * s^(n-1) * (1-s)^(s*n-1)), where s = 0.530402312512063468084914246777198746... is the root of the equation (1-s)*(2 + s + s*log(1-s)) = 1. - Vaclav Kotesovec, Aug 10 2014
MATHEMATICA
Flatten[{1, Table[n!*Sum[(n^(k-1)*(-1)^(n-2*k-1)*StirlingS1[n-k-1, k])/(n-k-1)!, {k, 1, n-1}], {n, 2, 20}]}] (* Vaclav Kotesovec, Aug 10 2014 after Vladimir Kruchinin *)
PROG
(Maxima) a(n):=if n=1 then 1 else (n!*sum((n^(k-1)*(-1)^(n-2*k-1)*stirling1(n-k-1, k))/(n-k-1)!, k, 1, n-1));
(PARI) a(n) = if (n==1, 1, n!*sum(k=1, n-1, (n^(k-1)*(-1)^(n-2*k-1)*stirling(n-k-1, k, 1))/(n-k-1)!)); \\ Michel Marcus, Oct 13 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladimir Kruchinin, Jun 01 2011
STATUS
approved