A177585 - OEIS

%I #3 Mar 31 2012 12:35:44

%S 1,6,90,2446,105516,6624618,570683441,64611629712,9304151482673,

%T 1660908411640448

%N Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down, up, down, up, up

%K nonn

%O 1,2

%A _R. H. Hardin_ May 10 2010