A218200 Hilltop maps: number of n X 2 binary arrays indicating the locations of corresponding elements not exceeded by any horizontal or vertical neighbor in a random 0..2 n X 2 array.

3, 15, 59, 233, 929, 3697, 14719, 58599, 233291, 928769, 3697573, 14720617, 58605079, 233315983, 928867415, 3697966433, 14722182653, 58611311377, 233340796147, 928966198975, 3698359708575, 14723748344241, 58617544637937

Offset

1,1

Comments

Column 2 of A218206.

Links

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

Formula

Empirical: a(n) = 3*a(n-1) + 3*a(n-2) + 3*a(n-3) + 2*a(n-4) + 2*a(n-5) - a(n-6) - a(n-7) - a(n-8) - a(n-9).

Empirical g.f.: x*(3 + 6*x + 5*x^2 + 2*x^3 + 2*x^4 - 2*x^5 - 3*x^6 - 2*x^7 - x^8) / (1 - 3*x - 3*x^2 - 3*x^3 - 2*x^4 - 2*x^5 + x^6 + x^7 + x^8 + x^9). - Colin Barker, Mar 09 2018

Example

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

Crossrefs

Cf. A218206.

Sequence in context: A049150 A309564 A062473 * A069009 A328104 A179604

Adjacent sequences: A218197 A218198 A218199 * A218201 A218202 A218203

Keyword

nonn

Author

R. H. Hardin, Oct 23 2012

Status

approved