A218313 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..2 n X 2 array.

3, 15, 63, 249, 993, 3969, 15867, 63423, 253503, 1013265, 4050081, 16188417, 64706067, 258633999, 1033775487, 4132062153, 16516098369, 66015828225, 263869194699, 1054700876799, 4215702180735, 16850412536481, 67352101850817

Offset

1,1

Comments

Column 2 of A218319.

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).

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

Example

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

Crossrefs

Cf. A218319.

Sequence in context: A204086 A171761 A229277 * A218190 A216757 A218366

Adjacent sequences: A218310 A218311 A218312 * A218314 A218315 A218316

Keyword

nonn

Author

R. H. Hardin, Oct 25 2012

Status

approved