A274750 Number of 3 X n 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.

2, 9, 34, 133, 518, 2017, 7858, 30605, 119214, 464345, 1808682, 7044997, 27441030, 106885713, 416331266, 1621654589, 6316517406, 24603508041, 95833284570, 373280851061, 1453968675382, 5663362861249, 22059401583154, 85923718843693

Offset

1,1

Links

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

Formula

Empirical: a(n) = 2*a(n-1) + 7*a(n-2) + 2*a(n-3) - 2*a(n-4).

Empirical g.f.: x*(2 + 5*x + 2*x^2 - 2*x^3) / ((1 + x)*(1 - 3*x - 4*x^2 + 2*x^3)). - Colin Barker, Jan 30 2019

Example

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

Crossrefs

Row 3 of A274749.

Sequence in context: A010763 A077234 A091526 * A204444 A204430 A150937

Adjacent sequences: A274747 A274748 A274749 * A274751 A274752 A274753

Keyword

nonn

Author

R. H. Hardin, Jul 04 2016

Status

approved