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 A158044 #9 Nov 27 2015 00:33:38 %S A158044 720,8482320,23846746320,46069117007760,78423934939027920, %T A158044 126377664053739048720,199725313669091369807760, %U A158044 316583663401497456387173520,508625335390476191389947899280 %N A158044 Determinant of power series of gamma matrix with determinant 6!. %C A158044 a(n) = Determinant(A + A^2 + A^3 + A^4 + A^5 + ... + A^n) %C A158044 where A is the submatrix A(1..7,1..7) of the matrix with factorial determinant %C A158044 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 A158044 G. Balzarotti and P. P. Lava, Le sequenze di numeri interi, Hoepli, 2008 %e A158044 a(1) = Determinant(A) = 6! = 720. %p A158044 seq(Determinant(sum(A^i,i=1..n)),n=1..30); %Y A158044 Cf. A111490, A158040, A158041, A158042, A158043. %K A158044 nonn %O A158044 0,1 %A A158044 _Giorgio Balzarotti_ & _Paolo P. Lava_, Mar 11 2009