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A208309 Number of n X 3 0..1 arrays with new values 0..1 introduced in row major order and no element equal to more than one of its immediate leftward or upward neighbors. 1
4, 18, 78, 336, 1446, 6222, 26772, 115194, 495654, 2132688, 9176478, 39484326, 169892196, 731008002, 3145363422, 13533793104, 58232875254, 250562996958, 1078116359028, 4638892804266, 19960114944246, 85883896308432 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 3 of A208314.

LINKS

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

FORMULA

Empirical: a(n) = 5*a(n-1) - 3*a(n-2).

Conjectures from Colin Barker, Jun 30 2018: (Start)

G.f.: 2*x*(2 - x) / (1 - 5*x + 3*x^2).

a(n) = (2^(-n)*((5-sqrt(13))^n*(-7+sqrt(13)) + (5+sqrt(13))^n*(7+sqrt(13)))) / (3*sqrt(13)).

(End)

EXAMPLE

Some solutions for n=4:

..0..1..0....0..0..0....0..1..1....0..1..1....0..1..1....0..1..0....0..0..0

..1..0..1....1..0..1....1..0..1....1..0..0....0..1..0....1..0..1....0..1..1

..0..1..0....0..1..0....1..1..0....1..1..1....0..1..1....1..0..1....1..0..1

..1..0..1....0..0..1....1..0..1....1..0..1....0..1..0....1..1..0....0..1..0

CROSSREFS

Cf. A208314.

Sequence in context: A219436 A219137 A240342 * A112619 A196810 A177755

Adjacent sequences:  A208306 A208307 A208308 * A208310 A208311 A208312

KEYWORD

nonn

AUTHOR

R. H. Hardin, Feb 25 2012

STATUS

approved

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Last modified October 6 12:35 EDT 2022. Contains 357264 sequences. (Running on oeis4.)