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 A068894 #6 Dec 05 2013 19:55:14
%S A068894 1,4,125,10556001,131068195168072318688258971724480032
%N A068894 a(1) = 1; a(n) is the smallest n-th power which is congruent to 1 mod a(n-1).
%e A068894 a(3) = 125 = 5^3 = 31*a(2) + 1 where a(2) = 4=2^2 = 3*1 + 1.
%o A068894 (PARI) v=vector(15):v[2]=4:print1("1,4,"):for(n=3,15, for(k=2,10^8,if(((k^n)%(v[n-1]))==1,print1(k^n","):v[n]=k^n:break)))
%K A068894 nonn
%O A068894 1,2
%A A068894 _Amarnath Murthy_, Mar 20 2002
%E A068894 Corrected and extended by _Ralf Stephan_, Mar 21 2003