%I #3 Mar 31 2012 12:35:44
%S 1,6,90,2512,112440,7367330,664573798,78969593280,11955422386863,
%T 2246458143581603
%N Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, up, down, up, up, up
%K nonn
%O 1,2
%A _R. H. Hardin_ May 10 2010