A026033 C(4n,n) - C(4n,n-4).

1, 4, 28, 220, 1819, 15484, 134320, 1180764, 10482340, 93766288, 843822148, 7631018564, 69291185474, 631334484200, 5769124912320, 52851389067420, 485242722376524, 4463782855666480, 41133265444555120

Offset: 0

Author

Clark Kimberling

Keywords

• nonn

Crossrefs

a(n) = T(4n, n), where T is defined in A026022.

Formula

G.f.: (g-2)*(2-2*g+g^2)*g^2/(3*g-4) where g = 1+x*g^4 is the g.f. of A002293. - Mark van Hoeij, Nov 11 2011

Extensions

More terms from Ralf Stephan, Jan 09 2005