%I #3 Mar 31 2012 12:35:36
%S 1,2,4,12,40,116,252,768,2704,12756,63168,338308,1956876,11971780,
%T 77909884,535178056,3906154920,30146769464,244980749052,2094507398508
%N Number of permutations of 1..n with all differences of elements separated by distances 1 or 2 being respectively unique.
%C (Empirical) Equals A008404 for n<=2m+2, where m is the maximum difference separation 2.
%K nonn
%O 1,2
%A _R. H. Hardin_ Dec 02 2009
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