OFFSET
0,3
FORMULA
a(n) = Sum_{k=0..n} (-1)^(n-k)*s(2*k,k).
a(n) ~ 2^(3*n-1) * c^(2*n) * n^(n - 1/2) / (sqrt(Pi*(c-1)) * (2*c-1)^n * exp(n)), where c = -LambertW(-1,-exp(-1/2)/2) = 1.7564312086261696769827376166... - Vaclav Kotesovec, Jul 05 2021
MAPLE
seq(sum((-1)^(n-k)*abs(combinat[stirling1](2*k, k)), k=0..n), n=0..12);
MATHEMATICA
Table[Sum[(-1)^(n-k)Abs[StirlingS1[2k, k]], {k, 0, n}], {n, 0, 15}]
PROG
(Maxima) makelist(sum((-1)^(n-k)*abs(stirling1(2*k, k)), k, 0, n), n, 0, 12);
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Emanuele Munarini, Mar 12 2011
STATUS
approved