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 A172086 #15 Apr 22 2021 16:25:35 %S A172086 2,-2,1,-1,-1,1,1,-1,-1,1,5,-5,-691,691,7,-7,-3617,3617,43867,-43867, %T A172086 -174611,174611,854513,-854513,-236364091,236364091,8553103,-8553103, %U A172086 -23749461029,23749461029,8615841276005,-8615841276005,-7709321041217,7709321041217,2577687858367,-2577687858367 %N A172086 Numerators of sum (C(n) = A051716/A051717) + (1 followed by first differences A172083/A051717 of Bernoulli numbers). %C A172086 Denominators: 1, 1, 3, 3, 15, 15, 21, 21, 15, 15, 33, 33, 1365, 1365, ... = A001897 with terms repeated. See A000367/A002445. %Y A172086 Cf. A000367, A001897, A002445, A027641, A051716, A051717 %K A172086 sign,frac %O A172086 0,1 %A A172086 _Paul Curtz_, Jan 25 2010 %E A172086 Name edited by _Michel Marcus_, Jan 30 2021 %E A172086 Clarified definition, added more terms. - _N. J. A. Sloane_, Apr 22 2021