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 A117547 #14 Feb 08 2015 04:35:57 %S A117547 0,2,11,12,70,408,2378,13860,80782,470832,2744210,15994428,93222358, %T A117547 543339720,3166815962,18457556052,107578520350,627013566048, %U A117547 3654502875938,21300003689580,124145519261542,723573111879672,4217293152016490,24580185800219268 %N A117547 Numbers n such that 2*n^2+1 is a perfect power. %C A117547 The value of y in the solution of the Diophantine equation x^a - 2*y^b = 1. All solutions have b=2. Sequence A075114 gives n^2. The only known solution for a>2 is y=11. See A075114 for more details. %F A117547 Conjecture: a(n) = 6*a(n-1) - a(n-2) for n>5; g.f.: x^2*(2-x-52*x^2+9*x^3)/ (1-6*x+x^2). - _Colin Barker_, Apr 28 2012 %o A117547 (PARI) %o A117547 Vec(x^2*(2-x-52*x^2+9*x^3)/ (1-6*x+x^2) + O(x^66)) %o A117547 /* _Joerg Arndt_, Apr 28 2012, using _Colin Barker_'s g.f. */ %K A117547 nonn %O A117547 1,2 %A A117547 _T. D. Noe_, Mar 29 2006 %E A117547 More terms from _T. D. Noe_, Nov 19 2006