A183247 Number of permutations of 1..2*n+4 with each element displaced by at least n.

265, 1708, 13365, 114124, 998112, 8751552, 76915200, 677461056, 5979015552, 52866428352, 468241962240, 4153739516736, 36900195503232, 328234303349952, 2923170205716480, 26061029280983616, 232569271090134912

Offset

1,1

Comments

Row 5 of A183244.

Links

R. H. Hardin, Table of n, a(n) for n = 1..35

Formula

Empirical (for n>=4): 85264*9^(n-4) + 7203*2^(3*n-10) + 48*5^(n-4). - Vaclav Kotesovec, Nov 27 2012

Conjectures from Colin Barker, Mar 27 2018: (Start)

G.f.: x*(265 - 4122*x + 17394*x^2 - 7150*x^3 - 29191*x^4 - 100844*x^5) / ((1 - 5*x)*(1 - 8*x)*(1 - 9*x)).

a(n) = 22*a(n-1) - 157*a(n-2) + 360*a(n-3) for n>6.

(End)

Example

Some permutations of 1-8 with minimum displacement 2:
(7,4,5,8,3,2,1,6) (8,6,5,7,1,3,4,2) (8,4,5,6,7,2,1,3) (3,7,1,6,8,4,2,5)
(8,4,6,2,7,3,5,1) (6,5,7,8,3,2,1,4) (3,7,6,8,2,1,5,4) (5,4,6,7,8,1,2,3)
(4,8,6,7,2,1,3,5) (6,7,5,8,2,1,4,3) (7,5,6,1,8,3,2,4) (3,8,5,2,7,1,4,6)
(4,7,1,2,8,3,5,6) (7,4,5,1,8,2,3,6) (7,6,5,2,8,3,4,1) (3,5,7,8,1,4,2,6)
(5,6,7,8,2,4,3,1) (7,5,6,8,2,1,3,4) (5,8,6,7,2,3,1,4) (3,6,8,1,7,4,2,5)

Crossrefs

Cf. A183244.

Sequence in context: A202416 A202471 A202464 * A094795 A023043 A211719

Adjacent sequences: A183244 A183245 A183246 * A183248 A183249 A183250

Keyword

nonn

Author

R. H. Hardin, Jan 03 2011

Status

approved