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 A243656 #7 May 05 2023 17:49:09 %S A243656 1,3,9,13,17,23,27,29,39,43,51,53,61,69,79,81,87,101,103,107,113,117, %T A243656 127,129,131,139,153,157,159,173,179,181,183,191,199,207,211,221,233, %U A243656 237,243,251,257,261,263,269,277,283,289,299,303,309 %N A243656 Positive integers primitively represented by x^2+3xy-y^2. %o A243656 (C++) // Will Jagy's C++ program Conway_Positive_Primitive (see A243655 for source code). %Y A243656 Cf. A035256, A243656, A243655. %K A243656 nonn %O A243656 1,2 %A A243656 _N. J. A. Sloane_, Jun 11 2014