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 A264348 #9 Nov 18 2015 05:58:41 %S A264348 257,401,577,697,761,1009,1129,1297,1393,1489,1601,1897,2081,2153, %T A264348 2177,2329,2713,2777,2857,2993,3121,3137,3281,3889,4001 %N A264348 Exceptional odd numbers D that do not admit a solution to the Pell equation x^2 - D y^2 = +8 with both x and y odd. %C A264348 These are the odd numbers 1 (mod 8), not a square, having in the composite case no prime factors 3 or 5 (mod 8), and the indefinite binary quadratic form x^2 - D*y^2 (with discriminant 4*D > 0) does not represent +8. %C A264348 The odd numbers D which admit proper solutions to the Pell equation x^2 - D*y^2 = +8 with both x and y odd are given by A263012. %Y A264348 Cf. A263011, A263012. %K A264348 nonn %O A264348 1,1 %A A264348 _Wolfdieter Lang_, Nov 17 2015