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 A012081 #4 Feb 24 2012 12:50:40 %S A012081 1,2,24,888,68352,8853888,1724221056,470304668928,171029448056832, %T A012081 79950698284462080,46709069479002931200,33347332565041919950848, %U A012081 28565775294718770340331520,28915860353300526164581613568 %N A012081 arcsinh(arcsin(tan(x)))=x+2/3!*x^3+24/5!*x^5+888/7!*x^7+68352/9!*x^9... %K A012081 nonn %O A012081 0,2 %A A012081 Patrick Demichel (patrick.demichel(AT)hp.com)