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

1,1

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 * A376012 A212718 A357846

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