A203969 Number of n X 2 0..2 arrays with every 1 immediately preceded by 0 to the left or above, and every 2 immediately preceded by 0 1 to the left or above

2, 7, 29, 106, 396, 1488, 5569, 20859, 78133, 292644, 1096125, 4105590, 15377699, 57598086, 215736791, 808054127, 3026612006, 11336343903, 42460908170, 159039700345, 595692067467, 2231197862121, 8357076036219, 31301894398172

Offset

1,1

Comments

Column 2 of A203975.

Links

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

Formula

Empirical: a(n) = 2*a(n-1) +3*a(n-2) +12*a(n-3) +4*a(n-4) +5*a(n-5) -9*a(n-6) -a(n-8) +a(n-9).

Empirical g.f.: x*(2 + 3*x + 9*x^2 + 3*x^3 + 5*x^4 - 8*x^5 - x^7 + x^8) / ((1 + x + x^2 - x^3)*(1 - 3*x - x^2 - 7*x^3 + x^4 + x^6)). - Colin Barker, Jun 06 2018

Example

Some solutions for n=5:
..0..1....0..1....0..1....0..1....0..0....0..0....0..0....0..0....0..0....0..0
..0..1....1..0....0..0....0..1....1..1....0..0....0..1....1..0....0..1....1..1
..0..0....0..1....0..1....1..0....0..1....0..1....1..2....2..1....0..1....0..0
..0..1....0..2....1..0....2..0....0..1....0..1....0..0....0..0....0..0....0..0
..0..0....0..1....2..0....0..0....1..0....0..1....0..0....0..1....1..1....1..1

Crossrefs

Cf. A203975.

Sequence in context: A166939 A261182 A155186 * A199581 A289609 A278815

Adjacent sequences: A203966 A203967 A203968 * A203970 A203971 A203972

Keyword

nonn

Author

R. H. Hardin, Jan 08 2012

Status

approved