A218587 Hilltop maps: number of n X 3 binary arrays indicating the locations of corresponding elements not exceeded by any horizontal or antidiagonal neighbor in a random 0..2 n X 3 array.

7, 57, 449, 3567, 28305, 224643, 1782855, 14149449, 112295673, 891223263, 7073103393, 56134970523, 445509522567, 3535741318617, 28061053779825, 222703718478543, 1767465563243697, 14027311885918707, 111326343684867783

Offset

1,1

Comments

Column 3 of A218592.

Links

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

Formula

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

Empirical g.f.: x*(7 + 8*x + x^2 + 4*x^3 + x^4) / (1 - 7*x - 7*x^2 - 3*x^3 - 3*x^4 - 3*x^5). - Colin Barker, Jul 24 2018

Example

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

Crossrefs

Cf. A218592.

Sequence in context: A202510 A042187 A201872 * A218838 A082310 A014990

Adjacent sequences: A218584 A218585 A218586 * A218588 A218589 A218590

Keyword

nonn

Author

R. H. Hardin, Nov 03 2012

Status

approved