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

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

Offset

1,2

Comments

Column 5 of A226441

Links

R. H. Hardin, Table of n, a(n) for n = 1..210

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

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

Status

approved