%I

%S 1,1,2,6,12,44,116,374,1428,5960,26016,120570,590598,3065372,16566508,

%T 92827128,542485764,3298228302,20696614200

%N Number of permutations of {1..n} with the sum of squared adjacent differences <= n*(n+1)/2.

%Y Cf. A180071.

%K nonn,hard,more

%O 0,3

%A _R. H. Hardin_, Aug 09 2010

%E a(17)-a(18) from _Donovan Johnson_, Oct 11 2010

%E a(0)-a(1) from _Alois P. Heinz_, Sep 02 2020