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 A012670 #7 Feb 24 2012 12:51:04 %S A012670 2,-128,253952,-2863136768,107451055603712,-10140668012798148608, %T A012670 2022780765718183801782272,-757569427466144902069404827648 %N A012670 arctan(tanh(x)*tan(x))=2/2!*x^2-128/6!*x^6+253952/10!*x^10... %F A012670 (-1)^n * 2^(6n+1) * A090681(n). %K A012670 sign %O A012670 0,1 %A A012670 Patrick Demichel (patrick.demichel(AT)hp.com)