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A229446 Number of 3 X n 0..2 arrays with horizontal differences mod 3 never 1, vertical differences mod 3 never -1, and rows and columns lexicographically nondecreasing. 1
8, 13, 22, 37, 60, 93, 138, 197, 272, 365, 478, 613, 772, 957, 1170, 1413, 1688, 1997, 2342, 2725, 3148, 3613, 4122, 4677, 5280, 5933, 6638, 7397, 8212, 9085, 10018, 11013, 12072, 13197, 14390, 15653, 16988, 18397, 19882, 21445, 23088, 24813, 26622, 28517 (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) = (1/3)*n^3 + (8/3)*n + 5.

Conjectures from Colin Barker, Sep 17 2018: (Start)

G.f.: x*(8 - 19*x + 18*x^2 - 5*x^3) / (1 - x)^4.

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

(End)

EXAMPLE

Some solutions for n=4:

..0..2..2..2....0..0..2..2....0..2..2..2....0..0..0..2....0..0..0..2

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

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

CROSSREFS

Row 3 of A229445.

Sequence in context: A269354 A195984 A019535 * A205704 A337212 A093023

Adjacent sequences:  A229443 A229444 A229445 * A229447 A229448 A229449

KEYWORD

nonn

AUTHOR

R. H. Hardin, Sep 23 2013

STATUS

approved

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Last modified June 13 00:57 EDT 2021. Contains 344980 sequences. (Running on oeis4.)