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 A158048 #9 Nov 27 2015 00:36:12 %S A158048 120,-3120,1657560,-462870720,94034430600,-34709926327440, %T A158048 7736751469771080,-2418878906762872320,634745166256592831640, %U A158048 -175970074271706846159600,49274372699370917797432920 %N A158048 Determinant of power series with alternate signs of gamma matrix with determinant 5!. %C A158048 a(n) = Determinant(A - A^2 + A^3 - A^4 + A^5 - ... - (-1)^n*A^n) %C A158048 where A is the submatrix A(1..6,1..6) of the matrix with factorial determinant %C A158048 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)!. %C A158048 a(n) is even with respect to signs of power of A. %D A158048 G. Balzarotti and P. P. Lava, Le sequenze di numeri interi, Hoepli, 2008. %e A158048 a(1) = Determinant(A) = 5! = 120. %p A158048 seq(Determinant(sum(A^i*(-1)^(i-1),i=1..n)),n=1..30); %Y A158048 Cf. A111490, A158040-A158047. %K A158048 sign %O A158048 0,1 %A A158048 _Giorgio Balzarotti_ & _Paolo P. Lava_, Mar 11 2009