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 A259057 #7 Dec 10 2016 22:37:33 %S A259057 -1,20,-560,20160,-887040,46126080,-2767564800,188194406400, %T A259057 -14302774886400,1201433090457600,-110531844322099200, %U A259057 11053184432209920000,-1193743918678671360000,138474294566725877760000,-17170812526274008842240000 %N A259057 One-third of the even-indexed entries of A259056. %C A259057 It is conjectured that this is an integer sequence. %C A259057 For the odd-indexed entries of A259056 see %C A259057 (-1)^(n-1)*A034976(n), n >= 1. %F A259057 a(n) = A259056(2*n)/3, n >= 1. %Y A259057 Cf. A034976, A259056. %K A259057 sign,easy %O A259057 1,2 %A A259057 _Wolfdieter Lang_, Jul 07 2015