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 A152720 #4 Mar 30 2012 17:34:28
%S A152720 -1,1,-1,3,-1,-1,5,-3,-1,-1,7,-5,-3,-1,-1,11,-7,-5,-3,-1,-1,13,-11,-7,
%T A152720 -5,-3,-1,-1,17,-13,-11,-7,-5,-3,-1,-1,19,-17,-13,-11,-7,-5,-3,-1,-1,
%U A152720 23,-19,-17,-13,-11,-7,-5,-3,-1,-1,29,-23,-19,-17,-13,-11,-7,-5,-3,-1,-1
%N A152720 A prime-based vector recursion: a(n)={Prime[n],Prime[n-1],-Prime[n-2],...,-1,-1}.
%C A152720 Row sums are: {-1, 0, 1, 0, -3, -6, -15, -24, -39, -54, -71,...}
%F A152720 a(n)={Prime[n],Prime[n-1],-Prime[n-2],...,-1,-1}.
%e A152720 {-1},
%e A152720 {1, -1},
%e A152720 {3, -1, -1},
%e A152720 {5, -3, -1, -1},
%e A152720 {7, -5, -3, -1, -1},
%e A152720 {11, -7, -5, -3, -1, -1},
%e A152720 {13, -11, -7, -5, -3, -1, -1},
%e A152720 {17, -13, -11, -7, -5, -3, -1, -1},
%e A152720 {19, -17, -13, -11, -7, -5, -3, -1, -1},
%e A152720 {23, -19, -17, -13, -11, -7, -5, -3, -1, -1},
%e A152720 {29, -23, -19, -17, -13, -11, -7, -5, -3, -1, -1}
%t A152720 b[0] = {-1}; b[1] = {1, -1};
%t A152720 b[n_] := b[n] = Join[{Prime[n ]}, {-b[n - 1][[ 1]]}, Table[b[n - 1][[i]], {i, 2, Length[b[n - 1]]}]];
%t A152720 Table[b[n], {n, 0, 10}]; Flatten[%]
%Y A152720 A152568
%K A152720 tabl,sign
%O A152720 0,4
%A A152720 _Roger L. Bagula_, Dec 11 2008