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A229421 Number of n X n 0..2 arrays with horizontal differences mod 3 never 1, vertical differences mod 3 never -1, rows lexicographically nondecreasing, and columns lexicographically nonincreasing. 2
3, 12, 83, 754, 7816, 87648, 1037193, 12768612, 162034856, 2106287556, 27919532994, 376116911288, 5136301331502, 70961712401226, 990271481453131, 13940677426765198, 197768065242681646, 2824828320413979786, 40595088421065998006, 586585037559246948950 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Alois P. Heinz, Table of n, a(n) for n = 1..40

EXAMPLE

Some solutions for n=4

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

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

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

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

CROSSREFS

Diagonal of A229428.

Sequence in context: A023881 A067111 A171186 * A212718 A051549 A245775

Adjacent sequences:  A229418 A229419 A229420 * A229422 A229423 A229424

KEYWORD

nonn

AUTHOR

R. H. Hardin, Sep 22 2013

EXTENSIONS

a(16)-a(20) from Alois P. Heinz, Feb 08 2019

STATUS

approved

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Last modified October 23 11:52 EDT 2021. Contains 348212 sequences. (Running on oeis4.)