A160567 - OEIS

A160567

a(n)=4*(a(n-1)a(n-3)-a(n-2)^2)/a(n-4), a(1)=a(2)=a(3)=1, a(4)=-4.

%I #4 Feb 25 2015 14:26:00

%S 1,1,1,-4,-20,-144,704,34816,1101824,12124160,-4499439616,

%T -586464362496,-99309307559936,33947352788107264,26466630265219317760,

%U 25787111566764821970944,-7045529183328701486465024

%N a(n)=4*(a(n-1)a(n-3)-a(n-2)^2)/a(n-4), a(1)=a(2)=a(3)=1, a(4)=-4.

%C a(n+1) is the Hankel transform of A160565.

%p A160567 := proc(n)

%p option remember;

%p if n < 5 then

%p op(n,[1,1,1,-4]);

%p else

%p 4*(procname(n-1)*procname(n-3)-procname(n-2)^2)/procname(n-4) ;

%p end if;

%p end proc: # _R. J. Mathar_, Feb 25 2015

%Y Cf. A050512.

%K easy,sign

%O 0,4

%A _Paul Barry_, May 19 2009