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 A216550 #13 May 02 2013 13:07:59 %S A216550 7,13,19,31,43,61,79,127,199,313,2617,10501,12391,14479,138937,141079, %T A216550 986191 %N A216550 Numbers n such that (2^n+1)/3 is prime and can be written in the form a^2 + 3*b^2. %C A216550 The exponent is congruent to 1 mod 3. %H A216550 Samuel S. Wagstaff, Jr. <a href="http://homes.cerias.purdue.edu/~ssw/cun/index.html">The Cunningham Project</a> %Y A216550 Cf. A000978. %K A216550 nonn %O A216550 1,1 %A A216550 _V. Raman_, Sep 08 2012