A218658 Hilltop maps: number of n X 3 binary arrays indicating the locations of corresponding elements not exceeded by any king-move neighbor in a random 0..1 n X 3 array.

5, 57, 417, 3249, 25533, 199489, 1560161, 12202673, 95434773, 746388537, 5837454753, 45654295713, 357058903853, 2792531543489, 21840184444225, 170810481722657, 1335896257560101, 10447946710663673, 81712625405191841

Offset: 1

Author

R. H. Hardin, Nov 04 2012

Keywords

• nonn

Comments

Column 3 of A218663.

Examples

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

Links

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

Crossrefs

Cf. A218663.

Formula

Empirical: a(n) = 6*a(n-1) + 11*a(n-2) + 26*a(n-3) - 5*a(n-4) - 5*a(n-6).

Empirical g.f.: x*(5 + 27*x + 20*x^2 - 10*x^3 - 5*x^4 - 5*x^5) / (1 - 6*x - 11*x^2 - 26*x^3 + 5*x^4 + 5*x^6). - Colin Barker, Mar 10 2018