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 A090451 #4 Oct 10 2012 03:11:51 %S A090451 1,0,1,-2,21,-454,25285,-3606504,1328522713,-1270747453940, %T A090451 3169192850406441,-20676520009454537480,353872602524737587995341, %U A090451 -15925173912641846013871947522,1888348697181821236021540428910349,-591053910458037676348857289166882470064 %N A090451 Alternating row sums of triangle A090447. %F A090451 a(n)=sum(A090447(n, m)*(-1)^m, m=0..n), n>=0. %F A090451 A090450 (row sums). %K A090451 sign,easy %O A090451 0,4 %A A090451 _Wolfdieter Lang_, Dec 23 2003