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.

1, 1, 1, -4, -20, -144, 704, 34816, 1101824, 12124160, -4499439616, -586464362496, -99309307559936, 33947352788107264, 26466630265219317760, 25787111566764821970944, -7045529183328701486465024

Offset

0,4

Comments

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

Links

Table of n, a(n) for n=0..16.

Maple

A160567 := proc(n)
    option remember;
    if n < 5 then
        op(n, [1, 1, 1, -4]);
    else
        4*(procname(n-1)*procname(n-3)-procname(n-2)^2)/procname(n-4) ;
    end if;
end proc: # R. J. Mathar, Feb 25 2015

Crossrefs

Cf. A050512.

Sequence in context: A340903 A098541 A004204 * A034216 A144009 A301270

Adjacent sequences: A160564 A160565 A160566 * A160568 A160569 A160570

Keyword

easy,sign

Author

Paul Barry, May 19 2009

Status

approved