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%I #15 Nov 21 2013 12:50:08
%S 3,5,21,437,190965,36467631221,1329888126870853950837,
%T 1768602429992068534155014726612412013000565
%N a(0) = 3; thereafter, a(n) = a(n-1)^2 - 4.
%C This is to A001566 as 4 is to 2 (subtrahend). This is the k=4 row of the array A[k,0] = 3, A[k,n] = A[k,n-1]^2 - k; A186750 is the k=3 row; and A001566 is the k=2 row. A003096(n+1) is the k=1 row.
%e a(1) = a(0)^2 - 4 = 3^2 - 4 = 5, which is, like a(0), a prime.
%t NestList[#^2-4&,3,10] (* _Harvey P. Dale_, Mar 14 2011 *)
%Y Cf. A001566, A003096, A186750.
%K nonn,easy
%O 0,1
%A _Jonathan Vos Post_, Feb 26 2011