A263691 Number of length n arrays of permutations of 0..n-1 with each element moved by -2 to 2 places and every three consecutive elements having its maximum within 3 of its minimum.

1, 2, 6, 14, 14, 16, 22, 36, 56, 85, 125, 189, 285, 434, 655, 993, 1499, 2271, 3432, 5197, 7857, 11893, 17985, 27218, 41167, 62293, 94227, 142571, 215672, 326309, 493637, 746845, 1129845, 1709362, 2585999, 3912361, 5918843, 8954567, 13547048

Offset

1,2

Links

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

Formula

Empirical: a(n) = a(n-1) + a(n-2) - a(n-3) + a(n-4) for n>12.

Empirical g.f.: x*(1 + x + 3*x^2 + 7*x^3 - 5*x^4 - 8*x^5 - 2*x^7 - x^9 - 2*x^10 - x^11) / (1 - x - x^2 + x^3 - x^4). - Colin Barker, Jan 02 2019

Example

Some solutions for n=7:
..0....0....0....1....0....1....1....0....0....0....0....1....2....0....0....0
..1....1....2....0....2....0....0....3....1....1....1....0....0....1....2....1
..2....2....1....2....1....3....2....1....2....2....3....2....1....2....1....3
..3....4....3....3....4....2....3....2....4....3....2....3....3....3....4....2
..5....3....4....4....3....5....5....4....3....4....4....4....4....4....3....5
..4....5....6....5....6....4....6....5....6....5....5....6....5....6....5....4
..6....6....5....6....5....6....4....6....5....6....6....5....6....5....6....6

Crossrefs

Column 2 of A263693.

Sequence in context: A054588 A084106 A295987 * A160657 A222087 A293654

Adjacent sequences: A263688 A263689 A263690 * A263692 A263693 A263694

Keyword

nonn

Author

R. H. Hardin, Oct 23 2015

Status

approved