A170809 - OEIS

%I #3 Mar 31 2012 12:35:36

%S 1,2,4,12,40,116,200,444,864,3368,10936,38320,139848,534828,2230464,

%T 9802612,46188544,231210272,1213437504,6717614708,39002297800

%N Number of permutations of 1..n with all differences of elements separated by distances 1 through 3 being respectively unique.

%C (Empirical) Equals A008404 for n<=2m+2, where m is the maximum difference separation 3.

%K nonn

%O 1,2

%A _R. H. Hardin_ Dec 02 2009