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 A216533 #16 May 02 2013 13:03:36
%S A216533 5,53,293,641,3011
%N A216533 Numbers n such that (10^n + 1)/11 is prime, but cannot be written in the form a^2 + 7*b^2.
%C A216533 These exponents are congruent to {2, 4, 5} mod 6.
%H A216533 Samuel S. Wagstaff, Jr. <a href="http://homes.cerias.purdue.edu/~ssw/cun/index.html">The Cunningham Project</a>
%Y A216533 Cf. A001562.
%K A216533 nonn
%O A216533 1,1
%A A216533 _V. Raman_, Sep 08 2012