

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.


2



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

1,3


LINKS



EXAMPLE

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


PROG

(Maxima) a(n):=sum(p!*coeff(expand(product(sum(binomial(k1, kj)*(1)^(kj)* (t^j/j!), j, 1, k), k, 1, n)), t, p), p, n, n*(n+1)/2); // Tani Akinari, Sep 15 2012


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



