0,1

a(n) = Determinant( A+A^2+ A^3+ A^4+ A^5+... A^n)

where A is the submatrix A(1..4,1..4)= of the matrix with factorial determinant

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)!

"Le sequenze di numeri interi", G. Balzarotti, P.P. Lava, 2008, ed. Hoepli.

a(1)=Determinant(A)=3!=6

seq(Determinant(sum(A^i, i=1..n)), n=1..30);

A111490, A158040

Sequence in context: A086205 A042759 A099595 this_sequence A078207 A060871 A162137

Adjacent sequences: A158038 A158039 A158040 this_sequence A158042 A158043 A158044

nonn

Giorgio Balzarotti & Paolo P. Lava (greenblue(AT)tiscali.it), Mar 11 2009