login
A280803
Number of n X n 0..1 arrays with no element equal to more than two of its horizontal, vertical and antidiagonal neighbors, with the exception of exactly two elements, and with new values introduced in order 0 sequentially upwards.
0
0, 1, 56, 2146, 41931, 547197, 5219491, 39260363, 247768745, 1379016025, 7040775017
OFFSET
1,3
COMMENTS
Diagonal of A280810.
EXAMPLE
Some solutions for n=4
..0..1..0..1. .0..0..1..0. .0..0..1..0. .0..1..1..0. .0..1..0..1
..0..1..1..1. .0..1..1..1. .1..1..0..1. .1..0..0..0. .0..0..0..1
..0..1..0..0. .0..0..0..1. .0..0..1..0. .0..1..0..1. .1..1..1..0
..0..0..1..1. .1..1..0..1. .1..1..1..0. .0..1..1..0. .0..0..0..0
CROSSREFS
Cf. A280810.
Sequence in context: A111597 A111781 A221398 * A124101 A198948 A003696
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 08 2017
STATUS
approved