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 A012138 #5 Feb 24 2012 12:50:41 %S A012138 1,-1,-11,-349,-22455,-2465241,-416217603,-100729124469, %T A012138 -33198564667887,-14328891118054449,-7852649782447649403, %U A012138 -5329635152693662625805,-4388960085492355649955495 %N A012138 cos(arcsin(arctanh(x)))=1-1/2!*x^2-11/4!*x^4-349/6!*x^6-22455/8!*x^8... %Y A012138 Cf. A012251. %K A012138 sign %O A012138 0,3 %A A012138 Patrick Demichel (patrick.demichel(AT)hp.com)