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A183981
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1/4 the number of (n+1) X 5 binary arrays with all 2 X 2 subblock sums the same.
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1
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15, 17, 20, 26, 36, 56, 92, 164, 300, 572, 1100, 2156, 4236, 8396, 16652, 33164, 66060, 131852, 263180, 525836, 1050636, 2100236, 4198412, 8394764, 16785420, 33566732, 67125260, 134242316, 268468236, 536920076, 1073807372, 2147581964, 4295098380
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OFFSET
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1,1
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COMMENTS
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Column 4 of A183986.
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LINKS
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R. H. Hardin, Table of n, a(n) for n = 1..200
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FORMULA
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Empirical: a(n) = 3*a(n-1) - 6*a(n-3) + 4*a(n-4).
Conjectures from Colin Barker, Apr 08 2018: (Start)
G.f.: x*(15 - 28*x - 31*x^2 + 56*x^3) / ((1 - x)*(1 - 2*x)*(1 - 2*x^2)).
a(n) = 3*2^(n/2-1) + 2^(n-1) + 12 for n even.
a(n) = 2^(n-1) + 2^((n+1)/2) + 12 for n odd.
(End)
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EXAMPLE
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Some solutions for 7 X 5:
..0..1..0..1..0....0..0..0..0..1....0..1..0..1..0....0..1..0..1..0
..1..1..1..1..1....1..0..1..0..0....0..1..0..1..0....0..0..0..0..0
..0..1..0..1..0....0..0..0..0..1....1..0..1..0..1....1..0..1..0..1
..1..1..1..1..1....1..0..1..0..0....1..0..1..0..1....0..0..0..0..0
..1..0..1..0..1....0..0..0..0..1....0..1..0..1..0....1..0..1..0..1
..1..1..1..1..1....1..0..1..0..0....0..1..0..1..0....0..0..0..0..0
..1..0..1..0..1....0..0..0..0..1....1..0..1..0..1....1..0..1..0..1
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CROSSREFS
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Cf. A183986.
Sequence in context: A043704 A329177 A074748 * A155111 A124334 A002155
Adjacent sequences: A183978 A183979 A183980 * A183982 A183983 A183984
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KEYWORD
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nonn
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AUTHOR
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R. H. Hardin, Jan 08 2011
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STATUS
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approved
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