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

Author

R. H. Hardin, Oct 23 2015

Keywords

• nonn

Examples

			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
		

Links

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

Crossrefs

Column 2 of A263693.

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