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 A166376 #2 Mar 31 2012 14:40:02
%S A166376 2,5,2,5,17,2,13,37,2,5,5,5,13,2,41,101,2,61,5,29,2,5,17,197,2,113,
%T A166376 257,2,5,29,5,5,13,2,181,401,2,13,17,5,97,2,5,53,577,2,313,677,2,5,73,
%U A166376 5,157,2,421,17,53,2,13,37,5,5,41
%N A166376 Triangle in which n-th row (n>1) gives prime factors of n^2 + 1 with repetition.
%e A166376 Since 13^2+1 = 170 = 2*5*17, the three terms 2, 5, 17 appear in the sequence.
%o A166376 (PARI) row(n)={m=n^2+1;while(m!=1,p=factor(m)[1,1];print(p);m=m/p)}
%Y A166376 Cf. A027746 A002522
%K A166376 nonn,tabf
%O A166376 1,1
%A A166376 _Michael B. Porter_, Oct 13 2009