This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A279687 #4 Dec 17 2016 17:56:02 %S A279687 1,2,5,13,17,29,421,401,37,1877,41 %N A279687 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 A279687 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 A279687 a(10)^2+1 = 882 = 2 * 29^2. Both 2 and 29 have already appeared in the sequence, so it terminates. %Y A279687 Cf. A031439. %K A279687 nonn,fini,full %O A279687 0,2 %A A279687 _Franklin T. Adams-Watters_, Dec 17 2016