A319924 - OEIS

%I #8 Oct 03 2018 18:23:19

%S 1,3,13,61,281,1261,5545,24025,102961,437581,1847561,7759753,32449873,

%T 135207801,561632401,2326762801,9617286241,39671305741,163352435401,

%U 671560012201,2756930576401,11303415363241,46290177201841,189368906734801,773942488394401

%N a(n) = A143565(2n,n) for n > 0, a(0) = 1.

%H Alois P. Heinz, <a href="/A319924/b319924.txt">Table of n, a(n) for n = 0..1658</a>

%F a(n) = A143565(2n,n) for n > 0, a(0) = 1.

%F a(n) = 1 + 2 * A002457(n-1) = 1 + 2 * (2*n-1)!/(n-1)!^2 for n > 0, a(0) = 1.

%p a:= proc(n) option remember; `if`(n<2, 2*n+1,

%p       ((15*n^2-29*n+10)*a(n-1)-(6*n-2)*(2*n-3)*

%p        a(n-2))/((n-1)*(3*n-4)))

%p     end:

%p seq(a(n), n=0..30);

%Y Cf. A002457, A143565.

%K nonn

%O 0,2

%A _Alois P. Heinz_, Oct 01 2018