A190945 Number of permutations of the n*(n+1)/2 numbers (i copies of i | i=1..n), with no element equal to another within a distance of 1.

1, 1, 10, 1074, 1637124, 45156692400, 27230193578558160, 420296434943941609215120, 190200071567439616748736269178720, 2843464512159537301384360263178682136716160, 1562137388408002436396705025296003247844758163480828800

Offset: 1

Author

R. H. Hardin, May 24 2011

Keywords

• nonn

Examples

			All solutions for n=3
..3....3....3....3....3....2....1....3....3....2
..2....1....2....2....2....3....3....1....2....3
..3....3....1....3....3....2....2....2....3....1
..2....2....3....1....2....3....3....3....1....3
..1....3....2....2....3....1....2....2....3....2
..3....2....3....3....1....3....3....3....2....3
		

Links

• Seiichi Manyama, Table of n, a(n) for n = 1..36 (a(1)-a(13) from R. H. Hardin).

Programs

Maxima

a(n):=sum(p!*coeff(expand(product(sum(binomial(k-1,k-j)*(-1)^(k-j)* (t^j/j!),j,1,k),k,1,n)),t,p),p,n,n*(n+1)/2); /* Tani Akinari, Sep 15 2012 */