A183355 One quarter the number of nX3 1..4 arrays with no two neighbors of any element equal to each other

12, 144, 432, 1296, 3888, 11664, 34992, 104976, 314928, 944784, 2834352, 8503056, 25509168, 76527504, 229582512, 688747536, 2066242608, 6198727824, 18596183472, 55788550416, 167365651248, 502096953744, 1506290861232, 4518872583696

Offset

1,1

Comments

Column 3 of A183362

Links

R. H. Hardin, Table of n, a(n) for n = 1..200

Formula

Empirical: a(n)=3*a(n-1) for n>2

Example

Some solutions for 5X3 with a(1,1)=1
..1..1..4....1..1..2....1..4..2....1..2..4....1..1..4....1..3..3....1..2..4
..4..2..2....2..4..3....1..3..2....4..2..1....3..2..4....2..4..1....1..2..4
..3..3..1....2..4..3....2..3..4....4..3..3....3..2..1....2..4..1....3..3..1
..2..4..4....1..1..2....2..1..4....2..1..4....4..4..3....1..3..2....2..4..1
..1..1..3....4..3..2....4..1..3....3..1..4....2..1..3....1..3..2....1..4..2

Crossrefs

Sequence in context: A207370 A208015 A208557 * A267716 A207309 A207115

Adjacent sequences: A183352 A183353 A183354 * A183356 A183357 A183358

Keyword

nonn

Author

R. H. Hardin Jan 04 2011

Status

approved