A218236 Hilltop maps: number of n X 2 binary arrays indicating the locations of corresponding elements not exceeded by any king-move neighbor in a random 0..3 n X 2 array.

3, 15, 63, 255, 1017, 4065, 16257, 65025, 260091, 1040319, 4161087, 16643583, 66571281, 266272929, 1065042945, 4259976705, 17039126547, 68153385231, 272601057663, 1090354299903, 4361217485769, 17444071124289, 69773089368321

Offset

1,1

Comments

Column 2 of A218242.

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) + 3*a(n-4) + 3*a(n-5) + 3*a(n-6) + 3*a(n-7).

Empirical g.f.: 3*x*(1 + x)^2*(1 + x^2)^2 / (1 - 3*x - 3*x^2 - 3*x^3 - 3*x^4 - 3*x^5 - 3*x^6 - 3*x^7). - Colin Barker, Mar 10 2018

Example

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

Crossrefs

Cf. A218242.

Sequence in context: A218366 A359082 A359083 * A218282 A103454 A024036

Adjacent sequences: A218233 A218234 A218235 * A218237 A218238 A218239

Keyword

nonn

Author

R. H. Hardin, Oct 24 2012

Status

approved