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A249390
The number of down-up permutations of [n] where adjacent elements differ by at least 3.
3
1, 1, 0, 0, 0, 0, 1, 8, 68, 480, 3637, 27968, 231410, 2014784, 18789010, 185234176, 1943243785, 21501237248, 251589065328, 3093350098432, 40007001803593, 541652523341824, 7679190979467688, 113578314941202432
OFFSET
0,8
CROSSREFS
Cf. A245377 (at least 2), A249391, A249392, A249393, A127697 (non-alternating).
Sequence in context: A208947 A296670 A263477 * A190510 A282563 A163307
KEYWORD
nonn,more
AUTHOR
R. J. Mathar, Oct 27 2014
EXTENSIONS
a(17)-a(20) from Alois P. Heinz, Oct 27 2014
a(21) from Alois P. Heinz, Oct 28 2014
a(22)-a(23) from Max Alekseyev, Feb 20 2024
STATUS
approved