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 A131777 #5 Mar 30 2012 17:39:24 %S A131777 1,5,1,1,5,1,5,-3,10,1,1,5,3,10,1,5,-7,20,-1,15,1,1,5,1,20,10,15,1,5, %T A131777 -11,30,-15,50,6,20,1,1,5,-5,30,15,50,22,20,1,5,-15,40,-45,105,-9,100, %U A131777 18,25,1 %N A131777 5*A065941 - 4*A049310. %C A131777 Row sums = A022096(n-1). %F A131777 5*A065941 - 4*A049310 as infinite lower triangular matrices. %e A131777 First few rows of the triangle are: %e A131777 1; %e A131777 5, 1 %e A131777 1, 5, 1; %e A131777 5, -3, 10, 1; %e A131777 1, 5, 3, 10, 1; %e A131777 5, -7, 20, -1, 15, 1; %e A131777 1, 5, 1, 20, 10, 15, 1; %e A131777 ... %Y A131777 Cf. A131774, A131775, A131776, A065941, A049310, A022096. %K A131777 tabl,sign %O A131777 1,2 %A A131777 _Gary W. Adamson_, Jul 14 2007 %E A131777 Corrected A-number in row sums reference _R. J. Mathar_, Jun 16 2009