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.

3, 12, 83, 754, 7816, 87648, 1037193, 12768612, 162034856, 2106287556, 27919532994, 376116911288, 5136301331502, 70961712401226, 990271481453131, 13940677426765198, 197768065242681646, 2824828320413979786, 40595088421065998006, 586585037559246948950

Offset: 1

Author

R. H. Hardin, Sep 22 2013

Keywords

• nonn

Examples

			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
		

Links

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

Crossrefs

Diagonal of A229428.

Extensions

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