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A183980 1/4 the number of (n+1) X 4 binary arrays with all 2 X 2 subblock sums the same. 1
9, 11, 14, 20, 30, 50, 86, 158, 294, 566, 1094, 2150, 4230, 8390, 16646, 33158, 66054, 131846, 263174, 525830, 1050630, 2100230, 4198406, 8394758, 16785414, 33566726, 67125254, 134242310, 268468230, 536920070, 1073807366, 2147581958, 4295098374 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 3 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*(9 - 16*x - 19*x^2 + 32*x^3) / ((1 - x)*(1 - 2*x)*(1 - 2*x^2)).

a(n) = (3*2^(n/2) + 2^n + 12) / 2 for n even.

a(n) = 2^((n-5)/2+3) + 2^(n-1) + 6 for n odd.

(End

EXAMPLE

Some solutions for 5 X 4.

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

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

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

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

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

CROSSREFS

Cf. A183986.

Sequence in context: A307188 A209321 A212816 * A101754 A113339 A270190

Adjacent sequences:  A183977 A183978 A183979 * A183981 A183982 A183983

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 08 2011

STATUS

approved

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Last modified May 17 22:15 EDT 2021. Contains 343992 sequences. (Running on oeis4.)