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 A101901 #3 Mar 30 2012 18:36:44 %S A101901 1,2,4,10,30,110,484,2514,15142,104126,806772,6965090,66374766, %T A101901 692629618,7860173564,96428710490,1272217776422,17968286438066, %U A101901 270569090589308,4328163151246858,73311692500174358,1311041890981700358 %N A101901 Absolute row sums of triangular matrix A101897, in which column k equals column 0 of A101897^k and where the n-th row sums are zero for n>0. %Y A101901 Cf. A101897, A101898, A101899, A101900. %K A101901 nonn %O A101901 0,2 %A A101901 _Paul D. Hanna_, Dec 20 2004