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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.

A158045 Determinant of power series with alternate signs of gamma matrix with determinant 2!.

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%I A158045 #16 Nov 27 2015 00:34:52
%S A158045 2,0,26,0,502,0,10306,0,213902,0,4448666,0,92558182,0,1925894386,0,
%T A158045 40073418302,0,833837682506,0,17350295562262,0,361020847688866,0,
%U A158045 7512036585662702,0,156308684773943546,0,3252434233373292742,0,67675884159595889746,0
%N A158045 Determinant of power series with alternate signs of gamma matrix with determinant 2!.
%C A158045 a(n) = Determinant(A - A^2 + A^3 - A^4 + A^5 - ... - (-1)^n*A^n), where A is the submatrix A(1..3,1..3) of the matrix with factorial determinant
%C A158045 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 A158045 G. Balzarotti and P. P. Lava, Le sequenze di numeri interi, Hoepli, 2008.
%F A158045 Empirical g.f.: -2*x*(2*x^2 -1)*(4*x^4 -11*x^2 +1) / ((x -1)*(x +1)*(2*x -1)*(2*x +1)*(2*x^2 -5*x +1)*(2*x^2 +5*x +1)). - _Colin Barker_, Jul 13 2014
%e A158045 a(1) = Determinant(A) = 2! = 2.
%p A158045 seq(Determinant(sum(A^i*(-1)^(i-1),i=1..n)), n=1..30);
%o A158045 (PARI) vector(100, n, matdet(sum(k=1, n, [1,1,1 ; 1,2,1 ; 1,2,3]^k*(-1)^(k-1)))) \\ _Colin Barker_, Jul 13 2014
%Y A158045 Cf. A111490, A158040-A158044.
%K A158045 nonn
%O A158045 1,1
%A A158045 _Giorgio Balzarotti_ & _Paolo P. Lava_, Mar 11 2009
%E A158045 More terms, and offset changed to 1 by _Colin Barker_, Jul 13 2014