%I #5 Apr 07 2021 19:24:09
%S 1,2,6,16,54,232,936,3880,17302,81584,425550,2332858,13639774,
%T 84416970,555549406,3834425860,27937916790
%N Number of permutations of 1..n with all sums of 2 through 4 adjacent terms respectively unique.
%K nonn
%O 1,2
%A _R. H. Hardin_, Nov 11 2008