A183357 One quarter the number of n X 5 1..4 arrays with no two neighbors of any element equal to each other.

108, 2304, 3888, 9216, 24192, 57600, 137088, 331776, 802944, 1937664, 4675968, 11289600, 27257472, 65804544, 158864256, 383533056, 925932672, 2235398400, 5396727168, 13028852736, 31454434944, 75937722624, 183329877888

Offset: 1

Author

R. H. Hardin, Jan 04 2011

Keywords

• nonn

Comments

Column 5 of A183362.

Examples

			Some solutions for 7 X 5 with a(1,1)=1:
..1..1..2..4..1....1..2..2..3..3....1..2..2..3..3....1..1..3..4..1
..4..3..3..4..2....1..4..4..1..2....3..4..4..1..1....4..2..2..4..3
..2..2..1..1..3....2..3..3..1..2....2..1..3..2..2....3..3..1..1..2
..3..4..4..2..3....4..1..2..4..4....2..1..3..4..4....2..4..4..3..2
..1..1..3..2..1....3..1..2..3..3....3..4..2..1..1....1..1..2..3..1
..4..2..3..4..4....2..4..4..1..2....3..4..2..3..3....4..3..2..4..1
..3..2..1..1..2....2..3..3..1..4....2..1..1..4..2....2..3..1..4..2
		

Links

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

Crossrefs

Cf. A183362.

Formula

Empirical: a(n) = 2*a(n-1) + 2*a(n-3) + a(n-4) for n>7.

Empirical g.f.: 36*x*(3 + 58*x - 20*x^2 + 34*x^3 + 29*x^4 - 24*x^5 - 12*x^6) / ((1 + x^2)*(1 - 2*x - x^2)). - Colin Barker, Mar 28 2018