A218422 Hilltop maps: number of nX4 binary arrays indicating the locations of corresponding elements not exceeded by any horizontal, vertical or antidiagonal neighbor in a random 0..1 nX4 array.

9, 191, 2725, 41515, 629659, 9539915, 144597047, 2191517757, 33214850067, 503408006597, 7629705089721, 115636627121941, 1752601092641329, 26562609636801375, 402585753260380041, 6101632743611966643

Offset: 1

Author

R. H. Hardin Oct 28 2012

Keywords

• nonn

Comments

Column 4 of A218426

Examples

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

Links

• R. H. Hardin, Table of n, a(n) for n = 1..146

Formula

Empirical: a(n) = 9*a(n-1) +72*a(n-2) +284*a(n-3) +526*a(n-4) +890*a(n-5) +902*a(n-6) +1382*a(n-7) -553*a(n-8) +2141*a(n-9) -1904*a(n-10) +416*a(n-11) -53*a(n-12) -263*a(n-13) -38*a(n-14) +38*a(n-15) -6*a(n-16) -18*a(n-17) +16*a(n-18) -a(n-20) +a(n-21)