A268974 Number of 4Xn 0..2 arrays with some element plus some horizontally or antidiagonally adjacent neighbor totalling two not more than once.

81, 1728, 15552, 136080, 1125360, 9093528, 72081792, 563173128, 4349328912, 33272350344, 252534743280, 1904015932416, 14274182767248, 106487231224248, 791006745522096, 5853579437553624, 43172409083833728, 317460508504648992

Offset: 1

Author

R. H. Hardin, Feb 16 2016

Keywords

• nonn

Comments

Row 4 of A268971.

Examples

			Some solutions for n=4
..2..1..0..0. .0..0..1..2. .0..1..0..0. .2..1..0..0. .0..1..2..1
..0..0..1..2. .0..2..1..2. .0..0..0..0. .0..0..0..0. .2..1..0..0
..1..2..2..2. .1..0..1..0. .2..1..0..0. .1..0..1..1. .0..0..1..2
..2..1..0..0. .0..0..0..0. .2..1..0..1. .1..0..0..0. .1..0..0..0
		

Links

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

Crossrefs

Cf. A268971.

Formula

Empirical: a(n) = 18*a(n-1) -111*a(n-2) +282*a(n-3) -333*a(n-4) +180*a(n-5) -36*a(n-6) for n>12