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A183979 1/4 the number of (n+1) X 3 binary arrays with all 2 X 2 subblock sums the same. 1
6, 8, 11, 17, 27, 47, 83, 155, 291, 563, 1091, 2147, 4227, 8387, 16643, 33155, 66051, 131843, 263171, 525827, 1050627, 2100227, 4198403, 8394755, 16785411, 33566723, 67125251, 134242307, 268468227, 536920067, 1073807363, 2147581955, 4295098371 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 2 of A183986.

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 07 2018: (Start)

G.f.: x*(6 - 10*x - 13*x^2 + 20*x^3) / ((1 - x)*(1 - 2*x)*(1 - 2*x^2)).

a(n) = (3*2^(n/2) + 2^n + 6) / 2 for n even.

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

(End

EXAMPLE

Some solutions for 5 X 3.

..1..0..1....1..0..1....1..0..1....1..0..1....0..1..0....1..0..1....1..0..1

..0..1..0....1..1..1....0..1..0....0..0..0....0..1..0....1..0..1....1..0..1

..0..1..0....0..1..0....0..1..0....1..0..1....1..0..1....0..1..0....0..1..0

..0..1..0....1..1..1....1..0..1....0..0..0....1..0..1....0..1..0....1..0..1

..0..1..0....0..1..0....0..1..0....1..0..1....1..0..1....0..1..0....0..1..0

CROSSREFS

Cf. A183986.

Sequence in context: A048586 A080824 A100602 * A222175 A315856 A265360

Adjacent sequences:  A183976 A183977 A183978 * A183980 A183981 A183982

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 08 2011

STATUS

approved

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Last modified March 30 06:17 EDT 2020. Contains 333119 sequences. (Running on oeis4.)