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 A218710 #4 Nov 05 2012 12:18:24
%S A218710 0,4,38,1985,27493,390112,390112,96940388,3379649772,24306922095,
%T A218710 450044583893,5597937117454,28673959190179,3524407382568745,
%U A218710 13428985415474682,13428985415474682,5711417117604156904,91610966633729580058,6709533061724423693474
%N A218710 a(n) is smallest number such that a(n)^2 + 1 is divisible by 17^n.
%e A218710 a(4) = 27493 because 27493^2+1 = 2 * 5 ^ 2 * 17 ^ 4 * 181.
%t A218710 b=4;n17=17;jo=Join[{0,b},Table[n17=17*n17;b=PowerMod[b,17,n17];b=Min[b,n17-b],{99}]]
%Y A218710 Cf. A002522, A049532, A034939, A218709.
%K A218710 nonn
%O A218710 0,2
%A A218710 _Michel Lagneau_, Nov 04 2012