OFFSET
1,1
FORMULA
G.f.: (g+2)*(g-1)/g^2 where g = 1+x*g^4 is the g.f. of A002293. - Mark van Hoeij, Nov 11 2011
a(n) ~ 2^(8*n - 5/2) / (sqrt(Pi) * n^(3/2) * 3^(3*n - 1/2)). - Vaclav Kotesovec, Mar 12 2019
MATHEMATICA
Table[3/(8*n - 4)*Binomial[4*n, n], {n, 1, 20}] (* Vaclav Kotesovec, Mar 12 2019 *)
PROG
(PARI) a(n) = 3*binomial(4*n, n)/(8*n-4); \\ Michel Marcus, Mar 12 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
More terms from Vaclav Kotesovec, Mar 12 2019
STATUS
approved