

A136609


(1/(n!)^2) * number of ways to arrange the consecutive numbers 1...n^2 in an n X n matrix with determinant = 0.


3




OFFSET

1,3


COMMENTS

The computation of a(5) seems to be currently (Jan 2008) out of reach (compare with A088021(5)).


LINKS

Table of n, a(n) for n=1..4.


EXAMPLE

a(1)=0 because det((1))/=0, a(2)=0, because the only possible determinants of a matrix with elements {1,2,3,4} are +2, +5 and +10.


CROSSREFS

Cf. A001044, A046747, a(3)=A088215(0), a(4)=A136608(0), A221976.
Sequence in context: A222739 A060716 A116255 * A116246 A128670 A225522
Adjacent sequences: A136606 A136607 A136608 * A136610 A136611 A136612


KEYWORD

hard,more,nonn


AUTHOR

Hugo Pfoertner, Jan 21 2008


STATUS

approved



