OFFSET
0,2
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..200
FORMULA
Formula: a(n) = 1+sum(binomial(n,k)binomial(2k-1,k-1)(2k)!/k!,k=0..n).
Recurrence: for n>=3, a(n) = 1/n*(-2 +(32 - 48*n + 16*n^2)*a(n-3) + (-31 + 63*n - 32*n^2)*a(n-2) + (3 - 14*n + 16*n^2)*a(n-1) )
E.g.f.: exp(x) (1/2 + 1/Pi K(16x) ), where K(z) is the elliptic integral of the first kind (defined as in Mathematica).
a(n) ~ 16^n*n^(n-1/2)*exp(1/16-n)/sqrt(2*Pi). - Vaclav Kotesovec, Aug 09 2013
MAPLE
seq(1+add(binomial(n, k)*binomial(2*k-1, k-1)*(2*k)!/k!, k=1..n), n=0..20);
MATHEMATICA
Table[1 + Sum[Binomial[n, k]Binomial[2k-1, k-1](2k)!/k!, {k, 1, n}], {n, 0, 20}]
PROG
(Maxima) makelist(1+sum(binomial(n, k)*binomial(2*k-1, k-1)*(2*k)!/k!, k, 1, n), n, 0, 12);
(PARI) a(n) = 1+sum(k=0, n, binomial(n, k)*binomial(2*k-1, k-1)*(2*k)!/k!) \\ Charles R Greathouse IV, Feb 07 2017
CROSSREFS
KEYWORD
nonn,easy,nice
AUTHOR
Emanuele Munarini, Mar 11 2011
STATUS
approved