A221448 Hilltop maps: number of 3Xn binary arrays indicating the locations of corresponding elements not exceeded by any horizontal or antidiagonal neighbor in a random 0..1 3Xn array.

1, 31, 221, 1465, 10593, 76055, 543081, 3883061, 27769277, 198564543, 1419847869, 10152784401, 72598518713, 519122981715, 3712041493221, 26543328598837, 189800757263741, 1357189525524527, 9704721072833461, 69394590298217165

Offset: 1

Author

R. H. Hardin Jan 17 2013

Keywords

• nonn

Comments

Row 3 of A221446

Examples

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

Links

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

Formula

Empirical: a(n) = 5*a(n-1) +8*a(n-2) +46*a(n-3) +39*a(n-4) +69*a(n-5) -10*a(n-6) -38*a(n-7) -68*a(n-8) -40*a(n-9) +50*a(n-10) +18*a(n-11) -13*a(n-12) -7*a(n-13) +4*a(n-14) +2*a(n-15) -a(n-16) +a(n-17)