%I #3 Mar 31 2012 12:35:44
%S 1,6,84,2123,84034,4804627,375435365,38463186965,5004563283887,
%T 806386210926308
%N Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down, up, up
%K nonn
%O 1,2
%A _R. H. Hardin_ May 10 2010
|