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A233099 Number of 2 X n 0..3 arrays with no element x(i,j) adjacent to value 3-x(i,j) horizontally, diagonally or antidiagonally, top left element zero, and 1 appearing before 2 in row major order. 1
3, 11, 65, 386, 2315, 13886, 83315, 499886, 2999315, 17995886, 107975315, 647851886, 3887111315, 23322667886, 139936007315, 839616043886, 5037696263315, 30226177579886, 181357065479315, 1088142392875886 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

FORMULA

Empirical: a(n) = 6*a(n-1) + a(n-2) - 6*a(n-3) for n>4.

Conjectures from Colin Barker, Oct 07 2018: (Start)

G.f.: x*(3 - 7*x - 4*x^2 + 3*x^3) / ((1 - x)*(1 + x)*(1 - 6*x)).

a(n) = (24 + 25*6^n) / 84 for n even.

a(n) = (60 + 25*6^n) / 84 for n>1 and odd.

(End)

EXAMPLE

Some solutions for n=5:

..0..1..0..1..3....0..1..3..2..0....0..0..0..0..1....0..1..1..1..0

..0..0..1..1..3....0..2..0..1..0....1..0..1..0..1....0..0..1..0..1

CROSSREFS

Row 2 of A233098.

Sequence in context: A199135 A096655 A030226 * A132101 A280775 A303341

Adjacent sequences:  A233096 A233097 A233098 * A233100 A233101 A233102

KEYWORD

nonn

AUTHOR

R. H. Hardin, Dec 04 2013

STATUS

approved

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Last modified November 13 11:09 EST 2018. Contains 317133 sequences. (Running on oeis4.)