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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.
2
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
OFFSET
1,1
COMMENTS
Column 3 of A184048.
LINKS
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
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 08 2011
STATUS
approved