A198900 Number of n X 2 0..4 arrays with values 0..4 introduced in row major order and no element equal to any horizontal or vertical neighbor.

1, 4, 33, 380, 4801, 62004, 804833, 10459180, 135958401, 1767426404, 22976444833, 298693487580, 3883014452801, 50479185229204, 656229400008033, 8530982176189580, 110902768218720001, 1441735986628126404

Offset

1,2

Comments

Column 2 of A198906.

Links

R. H. Hardin, Table of n, a(n) for n = 1..200

Formula

Empirical: a(n) = 17*a(n-1) -55*a(n-2) +39*a(n-3).

Conjectures from Colin Barker, Feb 18 2018: (Start)

G.f.: x*(1 - 13*x + 20*x^2) / ((1 - x)*(1 - 3*x)*(1 - 13*x)).

a(n) = (26 + 13*3^n + 13^n) / 78.

(End)

Example

Some solutions with values 0 to 4 for n=4:
..0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1
..2..3....2..3....2..0....1..2....1..0....2..3....2..3....2..3....1..2....2..3
..4..2....1..4....3..2....3..1....2..3....1..4....3..1....4..2....2..3....4..0
..2..4....3..2....4..3....2..4....4..2....4..3....4..2....2..0....4..0....0..3

Crossrefs

Sequence in context: A208961 A113170 A187738 * A166906 A293020 A293193

Adjacent sequences: A198897 A198898 A198899 * A198901 A198902 A198903

Keyword

nonn

Author

R. H. Hardin, Oct 31 2011

Status

approved