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%I #4 Dec 17 2016 17:56:02
%S 1,2,5,13,17,29,421,401,37,1877,41
%N a(0) = 1, a(n) is the least prime factor of a(n-1)^2+1 that has not previously appeared in the sequence for n > 0.
%e a(7) is a prime factor of a(6)^2+1 = 421^2 + 1 = 177242, which factors as 2*13*17*401. 2, 13, and 17 have already appeared in the sequence, so a(7) = 401.
%e a(10)^2+1 = 882 = 2 * 29^2. Both 2 and 29 have already appeared in the sequence, so it terminates.
%Y Cf. A031439.
%K nonn,fini,full
%O 0,2
%A _Franklin T. Adams-Watters_, Dec 17 2016
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