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 A158042 #11 Nov 27 2015 00:32:32 %S A158042 24,7200,671832,42120000,2259461784,116697218400,6145075369464, %T A158042 334042684560000,18529848376972632,1033842723079716000, %U A158042 57545200744624079544,3188945939520159000000,176129265145080634433304 %N A158042 Determinant of power series of gamma matrix with determinant 4!. %C A158042 a(n) = Determinant(A + A^2 + A^3 + A^4 + A^5 + ... + A^n) %C A158042 where A is the submtrix A(1..5,1..5) of the matrix with factorial determinant %C A158042 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 A158042 G. Balzarotti and P. P. Lava, Le sequenze di numeri interi, Hoepli, 2008. %e A158042 a(1) = Determinant(A) = 4! = 24. %p A158042 seq(Determinant(sum(A^i,i=1..n)),n=1..30); %Y A158042 Cf. A111490, A158040, A158041. %K A158042 nonn %O A158042 0,1 %A A158042 _Giorgio Balzarotti_ & _Paolo P. Lava_, Mar 11 2009