A216986 Number of city-block distance 1, pressure limit 2 movements in an nX3 array with each element moving exactly one horizontally or vertically, no element acquiring more than two neighbors, and without 2-loops.

0, 14, 264, 4794, 83304, 1435808, 24673352, 423651134, 7272419728, 124829530972, 2142624332680, 36776621687102, 631243274484392, 10834813398096496, 185971344332908696, 3192056733158039014, 54789226054169999632

Offset

1,2

Comments

Column 3 of A216991

Links

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

Formula

Empirical: a(n) = 24*a(n-1) -121*a(n-2) +28*a(n-3) +649*a(n-4) -844*a(n-5) +175*a(n-6) +80*a(n-7) -2*a(n-8)

Example

Some solutions for n=3 (movement: 0=n 1=e 2=s 3=w)
..1..1..2....1..2..3....1..1..2....2..3..3....1..1..2....2..3..3....1..2..2
..1..0..3....0..1..0....1..0..2....1..2..0....0..0..3....2..3..0....0..3..3
..0..3..3....0..3..0....1..0..3....0..3..3....1..0..3....1..1..0....0..1..0

Crossrefs

Sequence in context: A304189 A115611 A205467 * A138560 A051690 A048668

Adjacent sequences: A216983 A216984 A216985 * A216987 A216988 A216989

Keyword

nonn

Author

R. H. Hardin, Sep 21 2012

Status

approved