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

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

Offset

1,2

Comments

Column 4 of A226441

Links

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

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

Sequence in context: A177524 A223905 A164872 * A224287 A248838 A364231

Adjacent sequences: A226434 A226435 A226436 * A226438 A226439 A226440

Keyword

nonn

Author

R. H. Hardin Jun 06 2013

Status

approved