A026638 T(2n,n), T given by A026637.

1, 2, 8, 26, 92, 332, 1220, 4538, 17036, 64412, 244928, 935684, 3588392, 13806704, 53271548, 206040506, 798600332, 3101109164, 12062148368, 46986821516, 183276382472, 715748620424, 2798274135368, 10951009023716, 42895901012792, 168167959150232, 659793819847040

Offset

0,2

Links

Vincenzo Librandi, Table of n, a(n) for n = 0..1000

Formula

From Vaclav Kotesovec, Oct 21 2012: (Start)

G.f.: 1/(2+x)+3/((2+x)*sqrt(1-4*x))-1

Recurrence: 2*n*a(n) = (7*n-4)*a(n-1) + 2*(2*n-1)*a(n-2)

a(n) ~ 2^(2*n+2)/(3*sqrt(Pi*n))

(End)

Mathematica

CoefficientList[Series[1/(2+x)+3/((2+x)*Sqrt[1-4*x])-1, {x, 0, 20}], x] (* Vaclav Kotesovec, Oct 21 2012 *)

Prog

(PARI)  x='x+O('x^66); Vec( 1/(2+x)+3/((2+x)*sqrt(1-4*x))-1 ) \\ Joerg Arndt, May 04 2013

Crossrefs

Sequence in context: A053956 A320802 A052543 * A307401 A067855 A301699

Adjacent sequences: A026635 A026636 A026637 * A026639 A026640 A026641

Keyword

nonn

Author

Clark Kimberling

Status

approved