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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, 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.
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: A098541 A376528 A004204 * A034216 A144009 A301270
KEYWORD
easy,sign
AUTHOR
Paul Barry, May 19 2009
STATUS
approved