A203830 Number of (n+1) X 4 0..2 arrays with every 2 X 2 subblock having equal diagonal elements or equal antidiagonal elements.

1125, 17289, 270333, 4238721, 66490965, 1043088057, 16363800045, 256713156657, 4027283591877, 63179519387625, 991152375416541, 15549074160922593, 243931925405440053, 3826773454026870297, 60033942027766295757

Offset: 1

Author

R. H. Hardin, Jan 06 2012

Keywords

• nonn

Comments

Column 3 of A203835.

Examples

			Some solutions for n=4:
..2..1..0..2....1..1..0..1....1..2..2..1....1..2..1..1....2..1..0..0
..2..2..1..0....2..1..1..0....2..0..2..2....1..1..1..0....1..1..1..0
..1..2..2..1....1..1..0..0....2..2..1..2....1..2..1..1....2..1..2..1
..0..1..2..2....2..1..1..0....1..2..2..1....0..1..2..1....2..2..2..2
..2..0..1..2....0..2..1..1....1..1..2..2....2..0..1..1....1..2..1..2
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..210

Crossrefs

Cf. A203835.

Formula

Empirical: a(n) = 19*a(n-1) -54*a(n-2) +32*a(n-3).

Empirical g.f.: 9*x*(125 - 454*x + 288*x^2) / (1 - 19*x + 54*x^2 - 32*x^3). - Colin Barker, Jun 05 2018