A218421 Hilltop maps: number of nX3 binary arrays indicating the locations of corresponding elements not exceeded by any horizontal, vertical or antidiagonal neighbor in a random 0..1 nX3 array.

5, 49, 357, 2725, 20793, 158429, 1207525, 9203377, 70144889, 534620525, 4074695269, 31055936969, 236697756661, 1804029548133, 13749697742817, 104795505274517, 798715588594961, 6087537722095689, 46397135660186377

Offset: 1

Author

R. H. Hardin Oct 28 2012

Keywords

• nonn

Comments

Column 3 of A218426

Examples

			Some solutions for n=3
..0..1..0....1..0..0....0..1..1....1..1..0....1..0..0....0..1..0....0..1..1
..1..1..1....1..1..0....0..0..0....0..1..1....0..0..1....1..0..1....0..0..0
..1..1..1....1..0..1....0..1..1....0..1..1....1..0..0....0..0..0....1..1..0
		

Links

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

Formula

Empirical: a(n) = 5*a(n-1) +16*a(n-2) +28*a(n-3) +17*a(n-4) +7*a(n-5) -3*a(n-6) +3*a(n-7) -8*a(n-8) -a(n-10) +a(n-11)