A226437 Number of permutations of {1..n} with fewer than 4 interior elements having values lying between the values of their neighbors.

1, 1, 2, 6, 24, 120, 718, 4914, 37300, 308460, 2748354, 26194542, 265691456, 2856606480, 32449828310, 388371994890, 4885210675692, 64439603536980, 889564376280586, 12827733624005958, 192897097090449208, 3020051018689640760, 49155675298520617182, 830625328754347651746

Offset

0,3

Links

Alois P. Heinz, Table of n, a(n) for n = 0..482 (terms n = 1..210 from R. H. Hardin)

Example

Some solutions for n=8:
..3....8....1....8....2....4....2....8....4....5....8....7....6....6....7....2
..7....1....2....5....7....3....5....4....7....7....3....1....3....8....3....8
..1....2....8....6....3....8....4....7....8....1....4....4....7....4....4....6
..2....4....6....3....6....7....8....5....3....2....6....3....5....7....5....3
..8....5....3....1....8....2....1....1....2....4....1....2....4....3....6....5
..6....3....5....2....4....5....3....2....6....3....2....5....8....1....1....1
..4....6....4....7....5....6....6....3....5....8....7....6....2....5....8....4
..5....7....7....4....1....1....7....6....1....6....5....8....1....2....2....7

Crossrefs

Column 4 of A226441.

Sequence in context: A223905 A374620 A164872 * A224287 A248838 A364231

Adjacent sequences: A226434 A226435 A226436 * A226438 A226439 A226440

Keyword

nonn

Author

R. H. Hardin, Jun 06 2013

Extensions

a(0)=1 prepended by Alois P. Heinz, Jul 17 2024

Status

approved