A198976 Number of n X 2 0..5 arrays with values 0..5 introduced in row major order and no element equal to any horizontal or vertical neighbor.

1, 4, 34, 481, 8731, 174454, 3603244, 75251971, 1577395861, 33105096904, 695065679254, 14595390246661, 306496273473391, 6436373295247354, 135163500079092064, 2838431127851480551, 59607037068329713321

Offset: 1

Author

R. H. Hardin, Nov 01 2011

Keywords

• nonn

Comments

Column 2 of A198982.

Examples

			Some solutions with all values from 0 to 5 for n=4:
..0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1
..2..3....2..3....2..3....2..3....2..3....2..3....2..3....2..0....2..0....2..0
..4..5....4..2....1..4....0..4....4..5....4..0....4..5....3..1....3..4....3..4
..2..0....0..5....0..5....2..5....1..2....0..5....0..4....4..5....5..2....0..5
		

Links

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

Crossrefs

Cf. A198982.

Formula

Empirical: a(n) = 32*a(n-1) - 262*a(n-2) + 672*a(n-3) - 441*a(n-4).

Conjectures from Colin Barker, Feb 22 2018: (Start)

G.f.: x*(1 - 28*x + 168*x^2 - 231*x^3) / ((1 - x)*(1 - 3*x)*(1 - 7*x)*(1 - 21*x)).

a(n) = (189 + 56*3^n + 18*7^n + 21^n) / 504.

(End)