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

1,2

Comments

Diagonal of A280440.

Links

Table of n, a(n) for n=1..17.

Example

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.

Sequence in context: A157493 A192429 A354172 * A163697 A134424 A348621

Adjacent sequences: A280431 A280432 A280433 * A280435 A280436 A280437

Keyword

nonn

Author

R. H. Hardin, Jan 03 2017

Status

approved