A216984 Number of city-block distance 1, pressure limit 2 movements in an n X n array with each element moving exactly one horizontally or vertically, no element acquiring more than two neighbors, and without 2-loops.

0, 2, 264, 280900, 2891592224, 307860650044792, 342045101062468307160, 3979259269110908593906417328, 485168384985330726560602698774047840, 620116995791586597194849424436942942331423388, 8309613635077865959358673377383565557955823928354977328

Offset

1,2

Links

Table of n, a(n) for n=1..11.

Example

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

Crossrefs

Diagonal of A216991.

Sequence in context: A236437 A388297 A137105 * A007082 A135388 A238983

Adjacent sequences: A216981 A216982 A216983 * A216985 A216986 A216987

Keyword

nonn,more

Author

R. H. Hardin, Sep 21 2012

Status

approved