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 A216551 #13 May 02 2013 13:08:11 %S A216551 5,11,17,23,101,167,191,347,701,1709,3539,5807,10691,11279,42737, %T A216551 83339,95369,117239,127031,267017,269987,374321,4031399 %N A216551 Numbers n such that (2^n+1)/3 is prime, but cannot be written in the form a^2 + 3*b^2. %C A216551 The exponent is congruent to 2 mod 3. %H A216551 Samuel S. Wagstaff, Jr. <a href="http://homes.cerias.purdue.edu/~ssw/cun/index.html">The Cunningham Project</a> %Y A216551 Cf. A000978. %K A216551 nonn %O A216551 1,1 %A A216551 _V. Raman_, Sep 08 2012