A193808 Number of n X n symmetric 0..3 arrays with no element equal to the difference mod 4 of any two of its horizontal and vertical neighbors.

4, 23, 133, 1465, 37741, 2194501, 271424321, 68861945361, 35194944674859, 36030017205738273, 73787195288621907455, 302231516037239516908817, 2475880105112954130388596401, 40564819225226093549492737413585, 1329227995803738848421582217898872529, 87112285931790992384301674169215105553521

Offset

1,1

Links

R. H. Hardin, Table of n, a(n) for n = 1..20

Example

Some solutions for 4 X 4:
..3..3..3..1....1..1..1..3....3..3..1..1....1..1..1..1....1..2..1..2
..3..3..1..1....1..3..1..1....3..3..3..3....1..3..3..1....2..1..2..1
..3..1..3..1....1..1..3..3....1..3..1..1....1..3..3..3....1..2..1..2
..1..1..1..1....3..1..3..3....1..3..1..3....1..1..3..3....2..1..2..1

Crossrefs

Sequence in context: A227639 A291026 A239399 * A038723 A302761 A091640

Adjacent sequences: A193805 A193806 A193807 * A193809 A193810 A193811

Keyword

nonn

Author

R. H. Hardin, Aug 05 2011

Status

approved