A193808 - OEIS

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

(list; graph; refs; listen; history; text; internal format)

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