%I #3 Mar 31 2012 12:35:36
%S 1,2,4,12,40,116,200,444,760,2160,4872,11932,29252,71708,191356,
%T 536908,1607592,5184252,17331516,61597568,228854684,891958912
%N Number of permutations of 1..n with all differences of elements separated by distances 1 through 4 being respectively unique.
%C (Empirical) Equals A008404 for n<=2m+2, where m is the maximum difference separation 4.
%K nonn
%O 1,2
%A _R. H. Hardin_ Dec 02 2009