OFFSET
0,3
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..379
FORMULA
a(n) = (n!/2^n)*A098453(n);
a(n) = (n!/2^n)*Sum_{k=0..floor(n/2)} binomial(n, k)*binomial(2*(n-k), n)*3^k.
D-finite with recurrence: a(n) +(1-2n)*a(n-1) -3(n-1)^2*a(n-2)=0. - R. J. Mathar, Dec 11 2011
a(n) = n! * A002426(n). - Anton Zakharov, Sep 14 2016
MATHEMATICA
Table[(n!/2^n) Sum[Binomial[n, k] Binomial[2 (n - k), n] 3^k, {k, 0, Floor[n/2]}], {n, 0, 17}] (* Michael De Vlieger, Sep 14 2016 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Sep 08 2004
STATUS
approved