A280434 Number of n X n 0..1 arrays with no element equal to more than one of its horizontal and vertical neighbors, with the exception of exactly one element, and with new values introduced in order 0 sequentially upwards.

0, 4, 21, 80, 225, 548, 1211, 2512, 4989, 9604, 18073, 33432, 61035, 110276, 197581, 351568, 621945

Offset: 1

Author

R. H. Hardin, Jan 03 2017

Keywords

• nonn

Comments

Diagonal of A280440.

Examples

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

Crossrefs

Cf. A280440.