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 A158047 #10 Nov 27 2015 00:35:48 %S A158047 24,144,13896,842400,36604920,2333944368,126441557448,6680853691200, %T A158047 387982670513688,20676854461594320,1158249535425969384, %U A158047 63778918790403180000,3507499386329443453752,194248225087593045241968 %N A158047 Determinant of power series with alternate signs of gamma matrix with determinant 4!. %C A158047 a(n) = Determinant(A - A^2 + A^3 - A^4 + A^5 - ... - (-1)^n*A^n) %C A158047 where A is the submatrix A(1..5,1..5) of the matrix with factorial determinant %C A158047 A = [[1,1,1,1,1,1,...], [1,2,1,2,1,2,...], [1,2,3,1,2,3,...], [1,2,3,4,1,2,...], [1,2,3,4,5,1,...], [1,2,3,4,5,6,...], ...]; note: Determinant A(1..n,1..n) = (n-1)!. %D A158047 G. Balzarotti and P. P. Lava, Le sequenze di numeri interi, Hoepli, 2008. %e A158047 a(1) = Determinant(A) = 4! = 24. %p A158047 seq(Determinant(sum(A^i*(-1)^(i-1),i=1..n)),n=1..30); %Y A158047 Cf. A111490, A158040-A158046. %K A158047 nonn %O A158047 0,1 %A A158047 _Giorgio Balzarotti_ & _Paolo P. Lava_, Mar 11 2009