A209726 1/4 the number of (n+1) X 8 0..2 arrays with every 2 X 2 subblock having distinct clockwise edge differences.

16, 17, 18, 20, 22, 26, 30, 38, 46, 62, 78, 110, 142, 206, 270, 398, 526, 782, 1038, 1550, 2062, 3086, 4110, 6158, 8206, 12302, 16398, 24590, 32782, 49166, 65550, 98318, 131086, 196622, 262158, 393230, 524302, 786446, 1048590, 1572878, 2097166

Offset

1,1

Comments

Column 7 of A209727.

Links

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

Formula

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

Conjectures from Colin Barker, Jul 12 2018: (Start)

G.f.: x*(16 + x - 31*x^2) / ((1 - x)*(1 - 2*x^2)).

a(n) = 3*2^(n/2 - 1) + 14 for n even.

a(n) = 2^((n + 1)/2) + 14 for n odd.

(End)

Example

Some solutions for n=4:
..1..2..0..2..1..2..0..2....0..1..0..2..0..1..0..2....1..2..0..2..0..2..1..2
..2..0..1..0..2..0..1..0....2..0..2..1..2..0..2..1....2..0..1..0..1..0..2..0
..1..2..0..2..1..2..0..2....0..1..0..2..0..1..0..2....1..2..0..2..0..2..1..2
..2..0..1..0..2..0..1..0....2..0..2..1..2..0..2..1....2..0..1..0..1..0..2..0
..1..2..0..2..1..2..0..2....0..1..0..2..0..1..0..2....1..2..0..2..0..2..1..2

Crossrefs

Cf. A209727.

Sequence in context: A296754 A297284 A270043 * A326455 A145449 A138599

Adjacent sequences: A209723 A209724 A209725 * A209727 A209728 A209729

Keyword

nonn

Author

R. H. Hardin, Mar 12 2012

Status

approved