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 A020677 #14 Jun 08 2014 15:32:24
%S A020677 0,3,4,7,12,16,19,27,28,31,36,39,43,48,52,63,64,67,75,76,79,84,91,100,
%T A020677 103,108,111,112,124,127,139,144,147,148,151,156,163,171,172,175,183,
%U A020677 192,196,199,208,211,219,223,228,243,244,247,252,256,259,268,271,279,283,291
%N A020677 Numbers of form 3*x^2 + 4*y^2.
%C A020677 Each of these numbers is congruent to 0, 3, 4 or 7 mod 12. Therefore, except for 3, all the primes in this sequence are of the form 12k + 7. - _Alonso del Arte_, Jan 23 2014
%H A020677 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)
%t A020677 max = 300; Select[Union[Flatten[Table[3x^2 + 4y^2, {x, 0, Ceiling[Sqrt[max/3]]}, {y, 0, Ceiling[Sqrt[max/4]]}]]], # < max &] (* _Alonso del Arte_, Jan 23 2014 *)
%Y A020677 Cf. A068229.
%K A020677 easy,nonn
%O A020677 1,2
%A A020677 _David W. Wilson_