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%I #4 Mar 31 2012 12:36:20
%S 0,0,1,109,12721,2001240,418539642,113320421342,38733396860601,
%T 16350175635962731
%N Number of permutations of 3 copies of 1..n introduced in order 1..n with no element equal to another within a distance of 2
%e Some solutions for n=4
%e ..1....1....1....1....1....1....1....1....1....1....1....1....1....1....1....1
%e ..2....2....2....2....2....2....2....2....2....2....2....2....2....2....2....2
%e ..3....3....3....3....3....3....3....3....3....3....3....3....3....3....3....3
%e ..1....4....4....1....4....4....4....4....4....4....4....1....4....4....4....4
%e ..4....2....1....4....2....1....2....2....2....1....2....4....2....2....1....2
%e ..2....1....2....3....1....2....1....3....3....2....3....3....1....1....2....3
%e ..3....3....4....2....3....4....4....1....4....3....1....2....4....3....4....4
%e ..4....2....1....1....4....3....3....4....1....4....4....4....3....4....3....1
%e ..1....4....3....4....1....1....2....3....3....2....2....1....1....1....1....2
%e ..2....1....2....2....2....4....1....2....4....1....3....3....2....2....2....4
%e ..4....3....4....3....4....3....4....4....2....3....1....4....3....3....4....3
%e ..3....4....3....4....3....2....3....1....1....4....4....2....4....4....3....1
%K nonn
%O 1,4
%A _R. H. Hardin_ May 21 2011