A226438 Number of permutations of {1..n} with fewer than 5 interior elements having values lying between the values of their neighbors.

1, 1, 2, 6, 24, 120, 720, 5038, 40066, 353556, 3399246, 35142546, 387129588, 4515261680, 55502974820, 716557285110, 9689420220510, 136922907564972, 2018121531850482, 30972340185946810, 494190208052390752, 8186609585709287112, 140620153367124829272

Offset

0,3

Links

Alois P. Heinz, Table of n, a(n) for n = 0..481 (terms n = 1..210 from R. H. Hardin)

Example

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

Crossrefs

Column 5 of A226441.

Sequence in context: A193935 A177534 A164873 * A248839 A052399 A177553

Adjacent sequences: A226435 A226436 A226437 * A226439 A226440 A226441

Keyword

nonn

Author

R. H. Hardin, Jun 06 2013

Extensions

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

Status

approved