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 A152721 #3 Mar 30 2012 17:34:28
%S A152721 -1,1,-1,5,-1,-1,7,-5,-1,-1,11,-7,-5,-1,-1,13,-11,-7,-5,-1,-1,17,-13,
%T A152721 -11,-7,-5,-1,-1,19,-17,-13,-11,-7,-5,-1,-1,23,-19,-17,-13,-11,-7,-5,
%U A152721 -1,-1,29,-23,-19,-17,-13,-11,-7,-5,-1,-1,31,-29,-23,-19,-17,-13,-11,-7,-5
%N A152721 A prime based vector recursion: a(n)={Prime[n+1],Prime[n],Prime[n-1],-Prime[n-2],...,-1,-1}.
%C A152721 Row sums are:
%C A152721 {-1, 0, 3, 0, -3, -12, -21, -36, -51, -68, -95,...}
%F A152721 a(n)={Prime[n+1],Prime[n],Prime[n-1],-Prime[n-2],...,-1,-1}.
%e A152721 {-1},
%e A152721 {1, -1},
%e A152721 {5, -1, -1},
%e A152721 {7, -5, -1, -1},
%e A152721 {11, -7, -5, -1, -1},
%e A152721 {13, -11, -7, -5, -1, -1},
%e A152721 {17, -13, -11, -7, -5, -1, -1},
%e A152721 {19, -17, -13, -11, -7, -5, -1, -1},
%e A152721 {23, -19, -17, -13, -11, -7, -5, -1, -1},
%e A152721 {29, -23, -19, -17, -13, -11, -7, -5, -1, -1},
%e A152721 {31, -29, -23, -19, -17, -13, -11, -7, -5, -1, -1}
%t A152721 b[0] = {-1}; b[1] = {1, -1};
%t A152721 b[n_] := b[n] = Join[{Prime[n + 1 ]}, {-b[n - 1][[1]]}, Table[b[n - 1][[i]], {i, 2, Length[b[n - 1]]}]];
%t A152721 Table[b[n], {n, 0, 10}]; Flatten[%]
%Y A152721 A152568, A027293
%K A152721 sign
%O A152721 0,4
%A A152721 _Roger L. Bagula_, Dec 11 2008