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

1,2

Links

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

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

Example

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

Crossrefs

Column 2 of A263643.

Sequence in context: A189522 A210510 A050904 * A347305 A343878 A057471

Adjacent sequences: A263634 A263635 A263636 * A263638 A263639 A263640

Keyword

nonn

Author

R. H. Hardin, Oct 22 2015

Status

approved