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 A229384 #14 Sep 30 2013 17:32:27 %S A229384 1,1,13,239 %N A229384 Positive integer solutions y1, x1, y2, x2 to Ljunggren's equation x^2 + 1 = 2y^4. %C A229384 See the Wikipedia links for other references. %C A229384 The only square stella octangula numbers are A007588(1) = (a(1)*a(2))^2 = 1 and A007588(169) = (a(3)*a(4))^2 = 9653449. %D A229384 W. Ljunggren, Zur Theorie der Gleichung x^2 + 1 = Dy^4, Avh. Norske Vid. Akad. Oslo. I. 1942 (5): 27. %H A229384 Wikipedia, <a href="https://en.wikipedia.org/wiki/Stella_octangula_number">Stella octangula number</a> %H A229384 Wikipedia, <a href="https://en.wikipedia.org/wiki/Wilhelm_Ljunggren">Wilhelm Ljunggren</a> %e A229384 239^2 + 1 = 57122 = 2*13^4. %Y A229384 Cf. A007588. %K A229384 nonn,fini,full %O A229384 1,3 %A A229384 _Jonathan Sondow_, Sep 30 2013