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A184042 1/9 the number of (n+1) X 4 0..2 arrays with all 2 X 2 subblocks having the same four values. 1
25, 31, 41, 61, 97, 169, 305, 577, 1105, 2161, 4241, 8401, 16657, 33169, 66065, 131857, 263185, 525841, 1050641, 2100241, 4198417, 8394769, 16785425, 33566737, 67125265, 134242321, 268468241, 536920081, 1073807377, 2147581969, 4295098385 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 3 of A184048.

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..200

FORMULA

Empirical: a(n) = 3*a(n-1) - 6*a(n-3) + 4*a(n-4).

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

G.f.: x*(25 - 44*x - 52*x^2 + 88*x^3) / ((1 - x)*(1 - 2*x)*(1 - 2*x^2)).

a(n) = 3*2^(n/2) + 2^(n+1) + 17 for n even.

a(n) = 2^(n+1) + 2^((n+3)/2) + 17 for n odd.

(End)

EXAMPLE

Some solutions for 5 X 4:

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

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

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

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

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

CROSSREFS

Cf. A184048.

Sequence in context: A213929 A167324 A307283 * A157646 A198003 A039323

Adjacent sequences: A184039 A184040 A184041 * A184043 A184044 A184045

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 08 2011

STATUS

approved

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Last modified November 26 18:21 EST 2022. Contains 358362 sequences. (Running on oeis4.)