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 A180878 #2 Mar 30 2012 18:53:10
%S A180878 1,0,-1,-1,-9,-5,-21,-21,-197,-117,-427,-427,-2501,-1797,-2909,-2909,
%T A180878 -72877,-65453
%N A180878 Numerator in fraction A180878/A060818.
%C A180878 The generating function 1/sqrt((1/x-1)*(1/x+1)) is symmetrical around the origin and has singularities at -1 and +1.
%F A180878 Lambert series: Sum_{n >= 1} A180878(n)/A060818(n)*(x^n/(1-x^n)-x^(n+1)/(1-x^(n+1)))=1/sqrt((1/x-1)*(1/x+1)).
%Y A180878 Cf. Analogous to fraction A180403/A046161.
%K A180878 sign
%O A180878 1,5
%A A180878 _Mats Granvik_, Sep 23 2010