A263637 Number of length n arrays of permutations of 0..n-1 with each element moved by -2 to 2 places and with no two consecutive increases.

1, 2, 5, 9, 11, 19, 27, 44, 65, 104, 155, 246, 370, 582, 882, 1379, 2100, 3270, 4997, 7758, 11885, 18413, 28258, 43714, 67171, 103801, 159643, 246515, 379373, 585502, 901460, 1390734, 2141907, 3303555, 5089046, 7847557, 12090913, 18642253, 28725828

Offset: 1

Author

R. H. Hardin, Oct 22 2015

Keywords

• nonn

Examples

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

Links

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

Crossrefs

Column 2 of A263643.

Formula

Empirical: a(n) = 2*a(n-2) + a(n-3) - a(n-5) for n>9.

Empirical g.f.: x*(1 + x - x^2)*(1 + x + 3*x^2 + 2*x^3 - x^5 - x^6) / (1 - 2*x^2 - x^3 + x^5). - Colin Barker, Jan 02 2019