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 A213861 #12 Feb 01 2014 14:25:21
%S A213861 2,0,1,3,4,2949,8,11,12,15,17,115,20,7863275,24,27,16,73,32,35,25,39,
%T A213861 33,103,38,48589961800007,228,51,119,97,56,59,47,323,52,581,69,71,43,
%U A213861 2277,77,17509,80,75,84,87,68,133,92,95,2209,99,53,29363,104,107,6848,111,2585,3241,116,449,120,7847,78,1111,129,173,132,135,137,5340185
%N A213861 First occurrence of n in A213859.
%F A213861 a(n) = smallest k>n such that 2^k == n (mod k+2).
%e A213861 Smallest n such that A213859(n) = 7 is 11, so a(7) = 11.
%t A213861 nn = 25; t = Table[-1, {nn}]; Do[p = PowerMod[2, n, n + 2]; If[0 <= p <= nn && t[[p + 1]] == -1, t[[p + 1]] = n], {n, 0, 10^7}]; t (* _T. D. Noe_, Jun 26 2012 *)
%Y A213861 Cf. A213859, A213407, A036236
%K A213861 nonn
%O A213861 0,1
%A A213861 _Alex Ratushnyak_, Jun 22 2012
%E A213861 a(26)-a(50) from _T. D. Noe_, Jun 26 2012
%E A213861 Terms a(25) and a(51) onward from _Max Alekseyev_, Feb 01 2014