A274745 Number of n X 4 0..2 arrays with no element equal to any value at offset (-1,-2) (0,-1) or (-1,0) and new values introduced in order 0..2.

4, 22, 133, 813, 4967, 30349, 185435, 1133025, 6922887, 42299477, 258453699, 1579175897, 9648910127, 58955729261, 360224933899, 2201007512401, 13448358549783, 82170708943301, 502070597184787, 3067697574952457

Offset

1,1

Links

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

Formula

Empirical: a(n) = 6*a(n-1) + a(n-2) - 2*a(n-3) for n>4.

Empirical g.f.: x*(1 - x)*(4 + 2*x - x^2) / (1 - 6*x - x^2 + 2*x^3). - Colin Barker, Jan 30 2019

Example

Some solutions for n=4:
..0..1..2..1. .0..1..2..1. .0..1..0..2. .0..1..2..1. .0..1..0..2
..2..0..1..0. .2..0..1..2. .1..2..1..0. .1..0..1..0. .1..0..2..0
..1..2..0..1. .0..1..0..1. .2..1..2..1. .0..1..2..1. .0..2..0..2
..0..1..2..0. .2..0..2..0. .1..2..1..0. .2..0..1..2. .2..0..2..1

Crossrefs

Column 4 of A274749.

Sequence in context: A292838 A193620 A321275 * A197657 A183280 A183281

Adjacent sequences: A274742 A274743 A274744 * A274746 A274747 A274748

Keyword

nonn

Author

R. H. Hardin, Jul 04 2016

Status

approved