1,2

limit{n->oo} a(n)/(n^2)! = 1/e.

Leroy Quet, Home Page (listed in lieu of email address)

(n^2 -n)! (n^2 -n +1)! /(n^2 -2n +1)!

If n = 2, we have the permutations:

1,2,3,4; 1,4,3,2; 3,2,1,4; 3,4,1,2;

2,1,3,4; 4,1,3,2; 2,3,1,4; 4,3,1,2;

2,1,4,3; 4,1,2,3; 2,3,4,1; 4,3,2,1

(no multiples of 2 are adjacent in any of the permutations). So a(2) = 12.

a:=n->(n^2-n)!*(n^2-n+1)!/(n^2-2*n +1)!: seq(a(n), n=1..8); (Deutsch)

Sequence in context: A103482 A056540 A069048 this_sequence A055323 A013796 A055312

Adjacent sequences: A100243 A100244 A100245 this_sequence A100247 A100248 A100249

nonn

Leroy Quet Jan 11 2005

More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Aug 03 2005