A249391 The number of down-up permutations of [n] where adjacent elements differ by at least 4.

1, 1, 0, 0, 0, 0, 0, 0, 1, 16, 272, 2880, 32648, 333696, 3617545, 38942336, 443291226, 5168682752, 63523977424, 807890646528, 10790865576074, 149552304296960, 2168856599259491, 32631738808727552, 512002155247238968

Offset: 0

Author

R. J. Mathar, Oct 27 2014

Keywords

• nonn
• more

Crossrefs

Cf. A245377 (at least 2), A249390 (at least 3), A249392-A249393, A179957 (non-alternating).

Extensions

a(17)-a(20) from Alois P. Heinz, Oct 27 2014

a(21)-a(24) from Max Alekseyev, Feb 18 2024