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 A120901 #3 Mar 30 2012 18:36:58 %S A120901 1,1,5,14,43,156,535,1956,7175,26418,98375,367176,1378022,5193625, %T A120901 19641164,74535167,283651169,1082274210,4139129734,15863315213, %U A120901 60913982404,234317240601,902804442380,3483620505111,13460665855850 %N A120901 Central terms of triangle A120898 (cascadence of 1+2x+x^2). %Y A120901 Cf. A120898, A120899, A120900, A120902. %K A120901 nonn %O A120901 0,3 %A A120901 _Paul D. Hanna_, Jul 14 2006