A184689 1/3 the number of n X 4 0..2 arrays with no element equal both to the element above and to the element to its left.

27, 1536, 86688, 4890528, 275895264, 15564399648, 878052505824, 49534593003552, 2794452367733472, 157646678048909856, 8893504640414384352, 501719578033435638816, 28304087663951554461408, 1596751280124982805188128

Offset

1,1

Comments

Column 4 of A184694.

Links

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

Formula

Empirical: a(n) = 61*a(n-1) - 266*a(n-2) + 416*a(n-3) - 256*a(n-4).

Empirical g.f.: 3*x*(9 - 37*x + 58*x^2 - 32*x^3) / (1 - 61*x + 266*x^2 - 416*x^3 + 256*x^4). - Colin Barker, Apr 14 2018

Example

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

Crossrefs

Cf. A184694.

Sequence in context: A042404 A073224 A294964 * A364993 A059118 A211926

Adjacent sequences: A184686 A184687 A184688 * A184690 A184691 A184692

Keyword

nonn

Author

R. H. Hardin, Jan 20 2011

Status

approved