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 A172299 #3 Mar 30 2012 18:52:04 %S A172299 -2,2,-1,1,-1,1,-1,1,-1,25,-25,477481,-477481,49,-49,13082689, %T A172299 -13082689,1924313689,-1924313689,30489001321,-30489001321, %U A172299 730192467169,-730192467169,55867983514256281,-55867983514256281,73155570928609,-73155570928609 %N A172299 First differences of A172298. %C A172299 Differences between squares of Bernoulli number denominators. %F A172299 a(n) = A172298(n+1)-A172298(n). %F A172299 a(2n) = -a(2n-1), n>=2 . %K A172299 sign %O A172299 0,1 %A A172299 _Paul Curtz_, Jan 31 2010 %E A172299 Keyword:sign added, sequence extended by _R. J. Mathar_, Feb 02 2010