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%I #6 Feb 21 2022 12:53:09
%S 1,1,1,-9,-90,-1539,51759,7026831,1349328699,-119669884380,
%T -462804380329131,-818173230956710191,-775566981773559330471,
%U 23349606875054800260574779,383206716517298992863985977570
%N a(n)=9*(a(n-1)a(n-3)-a(n-2)^2)/a(n-4), a(1)=a(2)=a(3)=1, a(4)=-9.
%C a(n+1) is the Hankel transform of A160568.
%H Harvey P. Dale, <a href="/A160569/b160569.txt">Table of n, a(n) for n = 0..79</a>
%t nxt[{a_,b_,c_,d_}]:={b,c,d,(9(d*b-c^2))/a}; NestList[nxt,{1,1,1,-9},20][[All,1]] (* _Harvey P. Dale_, Feb 21 2022 *)
%Y Cf. A050512, A160566.
%K easy,sign
%O 0,4
%A _Paul Barry_, May 19 2009
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