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A183984 1/4 the number of (n+1) X 8 binary arrays with all 2 X 2 subblock sums the same. 1
81, 83, 86, 92, 102, 122, 158, 230, 366, 638, 1166, 2222, 4302, 8462, 16718, 33230, 66126, 131918, 263246, 525902, 1050702, 2100302, 4198478, 8394830, 16785486, 33566798, 67125326, 134242382, 268468302, 536920142, 1073807438, 2147582030 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 7 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 09 2018: (Start)

G.f.: x*(81 - 160*x - 163*x^2 + 320*x^3) / ((1 - x)*(1 - 2*x)*(1 - 2*x^2)).

a(n) = 3*2^(n/2-1) + 2^(n-1) + 78 for n even.

a(n) = 2^(n-1) + 2^((n+1)/2) + 78 for n odd.

(End)

EXAMPLE

Some solutions for 5 X 8.

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

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

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

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

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

CROSSREFS

Cf. A183986.

Sequence in context: A075691 A055390 A186472 * A089784 A186464 A295700

Adjacent sequences:  A183981 A183982 A183983 * A183985 A183986 A183987

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 08 2011

STATUS

approved

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Last modified March 19 00:15 EDT 2019. Contains 321306 sequences. (Running on oeis4.)