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A209530 Half the number of (n+1) X 3 0..2 arrays with every 2 X 2 subblock having exactly two distinct clockwise edge differences. 1
9, 25, 65, 193, 513, 1537, 4097, 12289, 32769, 98305, 262145, 786433, 2097153, 6291457, 16777217, 50331649, 134217729, 402653185, 1073741825, 3221225473, 8589934593, 25769803777, 68719476737, 206158430209, 549755813889 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 2 of A209534.

LINKS

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

FORMULA

Empirical: a(n) = a(n-1) + 8*a(n-2) - 8*a(n-3).

Conjectures from Colin Barker, Jul 10 2018: (Start)

G.f.: x*(9 + 16*x - 32*x^2) / ((1 - x)*(1 - 8*x^2)).

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

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

(End)

EXAMPLE

Some solutions for n=4:

..0..1..2....1..0..1....2..0..2....2..1..0....1..2..1....0..1..0....2..1..0

..1..2..1....2..1..2....0..2..0....1..2..1....2..1..2....1..0..1....1..2..1

..0..1..0....1..2..1....2..0..2....2..1..2....1..0..1....2..1..2....0..1..0

..1..0..1....2..1..2....0..2..0....1..2..1....2..1..2....1..0..1....1..2..1

..0..1..2....1..2..1....2..0..2....0..1..0....1..2..1....2..1..0....0..1..2

CROSSREFS

Cf. A209534.

Sequence in context: A111440 A077118 A242116 * A147392 A147318 A146589

Adjacent sequences:  A209527 A209528 A209529 * A209531 A209532 A209533

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 10 2012

STATUS

approved

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Last modified August 10 08:44 EDT 2020. Contains 336369 sequences. (Running on oeis4.)