A274798 Number of n X 3 0..2 arrays with no element equal to any value at offset (-1,-2) (-2,-1) (0,-1) or (-1,0) and new values introduced in order 0..2.

2, 8, 30, 112, 420, 1572, 5888, 22048, 82568, 309200, 1157904, 4336144, 16238112, 60808896, 227718752, 852767104, 3193464512, 11958969152, 44784259584, 167709263104, 628042022016, 2351908141824, 8807486941952, 32982506778880

Offset

1,1

Links

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

Formula

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

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

Example

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

Crossrefs

Column 3 of A274803.

Sequence in context: A278023 A077839 A052530 * A281949 A162551 A073663

Adjacent sequences: A274795 A274796 A274797 * A274799 A274800 A274801

Keyword

nonn

Author

R. H. Hardin, Jul 07 2016

Status

approved