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A193309

Number of n X n symmetric 0..3 arrays with no element equal to any horizontal or vertical neighbor, containing at least one 3 and with new values 0..3 introduced in lower triangular row major order.

0, 0, 20, 1436, 175145, 47175440, 29471424170, 42983780102348, 146444614636063181, 1165528963228211645900, 21669813287663490052945610, 941174635410184709958677112920, 95492317441878724418372856301818197

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

OFFSET

1,3

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..15

EXAMPLE

Some solutions for 4X4

..0..1..0..1....0..1..3..0....0..1..3..1....0..1..2..0....0..1..3..1

..1..2..1..3....1..2..0..2....1..2..1..3....1..2..3..2....1..2..1..3

..0..1..0..2....3..0..3..0....3..1..0..2....2..3..2..3....3..1..2..1

..1..3..2..1....0..2..0..3....1..3..2..3....0..2..3..0....1..3..1..2

CROSSREFS