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 A020684 #9 Jun 08 2014 15:35:40 %S A020684 0,4,9,13,16,25,36,40,45,52,64,72,73,81,85,97,100,109,117,136,144,145, %T A020684 148,153,160,180,181,196,205,208,225,229,232,241,244,256,261,265,277, %U A020684 288,289,292,324,325,328,333,337,340,360,369,388,400,405,409,421,424,436,441 %N A020684 Numbers of form 4 x^2 + 9 y^2. %H A020684 N. J. A. Sloane et al., <a href="https://oeis.org/wiki/Binary_Quadratic_Forms_and_OEIS">Binary Quadratic Forms and OEIS</a> (Index to related sequences, programs, references) %K A020684 easy,nonn %O A020684 1,2 %A A020684 _David W. Wilson_