A221088 Number of 2 X n arrays of occupancy after each element moves to some horizontal or antidiagonal neighbor.

0, 4, 24, 169, 1155, 7921, 54288, 372100, 2550408, 17480761, 119814915, 821223649, 5628750624, 38580030724, 264431464440, 1812440220361, 12422650078083, 85146110326225, 583600122205488, 4000054745112196, 27416783093579880

Offset

1,2

Comments

Row 2 of A221087.

Links

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

Formula

Empirical: a(n) = 7*a(n-1) - 7*a(n-3) + a(n-4).

Empirical g.f.: x^2*(2 - x)^2 / ((1 - x)*(1 + x)*(1 - 7*x + x^2)). - Colin Barker, Aug 03 2018

Example

Some solutions for n=3:
..0..1..0....0..1..1....1..2..0....1..3..1....1..1..0....1..3..0....1..2..1
..2..3..0....0..3..1....1..2..0....0..1..0....0..3..1....0..1..1....0..2..0

Crossrefs

Cf. A221087.

Sequence in context: A188913 A364324 A052685 * A365225 A369478 A368975

Adjacent sequences: A221085 A221086 A221087 * A221089 A221090 A221091

Keyword

nonn

Author

R. H. Hardin, Jan 01 2013

Status

approved