A185562 1/4 the number of n X 4 0..3 arrays with no element equal both to the element above and to the element to its left.

64, 13500, 2842560, 598507920, 126017211780, 26533211918040, 5586628402633500, 1176277376648694960, 247667889663690066720, 52147040135402715629580, 10979678466093753927519840, 2311796391622216326875508300

Offset: 1

Author

R. H. Hardin, Jan 31 2011

Keywords

• nonn

Comments

Column 4 of A185567.

Examples

			Some solutions for 3 X 4 with a(1,1)=0:
..0..0..2..0....0..0..3..0....0..2..0..2....0..0..3..1....0..2..2..0
..0..2..0..3....2..0..3..2....0..2..0..2....2..2..2..2....0..2..0..2
..0..3..3..2....2..2..1..2....2..3..2..1....0..3..0..0....0..2..3..2
		

Links

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

Crossrefs

Cf. A185567.

Formula

Empirical: a(n) = 217*a(n-1) - 1371*a(n-2) + 2835*a(n-3) - 2025*a(n-4).

Empirical g.f.: 4*x*(16 - 97*x + 201*x^2 - 135*x^3) / (1 - 217*x + 1371*x^2 - 2835*x^3 + 2025*x^4). - Colin Barker, Apr 16 2018