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 A195531 #21 Aug 22 2025 02:18:14 %S A195531 5,17,65,241,901,3361,12545,46817,174725,652081,2433601,9082321, %T A195531 33895685,126500417,472105985,1761923521,6575588101,24540428881, %U A195531 91586127425,341804080817,1275630195845,4760716702561,17767236614401,66308229755041 %N A195531 Hypotenuses of Pythagorean triples in A195499 and A195503. %C A195531 See A195500 for discussion and list of related sequences; see A195499 for Mathematica program. %C A195531 Essentially the same as A120893. - _R. J. Mathar_, Sep 21 2011 %F A195531 Conjecture: a(n) = 3*a(n-1)+3*a(n-2)-a(n-3). G.f.: x*(5+2*x-x^2)/((1+x)*(1-4*x+x^2)). - _Colin Barker_, Apr 08 2012 %Y A195531 Cf. A195500, A195499, A195503. %K A195531 nonn,changed %O A195531 1,1 %A A195531 _Clark Kimberling_, Sep 20 2011