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%I #4 Mar 31 2012 12:35:06
%S 0,0,1,1,8,3,136,29,928,942,66496,6175,2785856,205678,11122048
%N Half the number of permutations of 0..n with a zero n-th difference.
%e a(5)=3 because 0,1,2,3,4,5 ; 0,2,4,3,1,5 ; and 0,4,2,1,3,5 ; and their reverses have zero 5th differences.
%K nonn
%O 0,5
%A _R. H. Hardin_, Aug 13 2007
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