OFFSET
1,2
FORMULA
a(n) ~ sqrt(1-c) * 2^(2*n-1/2) * n^(n-3/2) / (sqrt(Pi) * exp(n) * (c*(2-c))^(n-1)), where c = -A226775 = -LambertW(-2*exp(-2)) = 0.4063757399599599... . - Vaclav Kotesovec, Jun 01 2015
a(n) = -Sum_{k=1..n} k^2*Bern(k-1)*C(2*n-1, k-1)*Stirling2(2*n-k, n), n>1, a(1)=1. - Vladimir Kruchinin, Jun 02 2015
MAPLE
seq(add(k^2*bernoulli(k-1)*binomial(2*n-1, k)*Stirling2(2*n-k, n), k=1..n), n=1..20); # Robert Israel, Jun 01 2015
MATHEMATICA
Table[Sum[k^2*BernoulliB[k-1]*Binomial[2*n-1, k]*StirlingS2[2*n-k, n], {k, 1, n}], {n, 1, 20}] (* Vaclav Kotesovec, Jun 01 2015 *)
PROG
(Maxima)
makelist(sum(k^2*bern(k-1)*binomial(2*n-1, k)*stirling2(2*n-k, n), k, 1, n), n, 1, 30);
(PARI) a(n) = sum(k=1, n, k^2*bernfrac(k-1)*binomial(2*n-1, k)*stirling(2*n-k, n, 2)); \\ Michel Marcus, Jun 01 2015
(Maxima)
makelist(if n=1 then 1 else -sum(k^2*bern(k-1)*binomial(2*n-1, k-1)*stirling2(2*n-k, n), k, 1, n), n, 1, 30); /* Vladimir Kruchinin, Jun 02 2015 */
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladimir Kruchinin, Jun 01 2015
STATUS
approved