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%I #3 Mar 31 2012 12:35:44
%S 1,6,90,2466,107556,6834976,596062132,68333017226,9966819746704,
%T 1802533316442602
%N Number of permutations of 2 copies of 1..n avoiding adjacent step pattern up, down, down, up, up, down
%K nonn
%O 1,2
%A _R. H. Hardin_ May 10 2010
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