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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 1
2, 7, 29, 106, 396, 1488, 5569, 20859, 78133, 292644, 1096125, 4105590, 15377699, 57598086, 215736791, 808054127, 3026612006, 11336343903, 42460908170, 159039700345, 595692067467, 2231197862121, 8357076036219, 31301894398172 (list; graph; refs; listen; history; text; internal format)
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

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Last modified September 17 06:41 EDT 2019. Contains 327119 sequences. (Running on oeis4.)