A280548 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 two elements, and with new values introduced in order 0 sequentially upwards.

0, 0, 50, 382, 1764, 6502, 20334, 56102, 141398, 332810, 743966, 1598198, 3328362, 6763114

Offset

1,3

Comments

Diagonal of A280554.

Links

Table of n, a(n) for n=1..14.

Example

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

Crossrefs

Cf. A280554.

Sequence in context: A184564 A184556 A334697 * A293608 A111341 A222693

Adjacent sequences: A280545 A280546 A280547 * A280549 A280550 A280551

Keyword

nonn

Author

R. H. Hardin, Jan 05 2017

Status

approved