A180071 Number of permutations of {1..n} with the sum of squared adjacent differences < n*(n+1)/2.

0, 1, 2, 6, 12, 24, 98, 344, 1236, 5332, 23772, 110962, 547714, 2840028, 15439466, 87299850, 512569668, 3111575102, 19577613014, 127331688104, 852129210498, 5853657714546, 41377621755100, 300511333393982, 2233952140321104

Offset

0,3

Links

Table of n, a(n) for n=0..24.

Crossrefs

Cf. A180070.

Sequence in context: A163895 A309016 A302652 * A034882 A175943 A228816

Adjacent sequences: A180068 A180069 A180070 * A180072 A180073 A180074

Keyword

nonn,hard

Author

R. H. Hardin, Aug 09 2010

Extensions

a(17)-a(18) from Donovan Johnson, Oct 11 2010

a(19) from Bert Dobbelaere, Aug 31 2020

a(0)-a(1) from Alois P. Heinz, Sep 02 2020

a(20)-a(23) from Martin Ehrenstein, Nov 12 2023

a(24) from Max Alekseyev, Mar 15 2024

Status

approved