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A224545
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Number of (n+1) X 4 0..1 matrices with each 2 X 2 subblock idempotent.
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1
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28, 52, 78, 125, 193, 302, 472, 743, 1175, 1868, 2982, 4777, 7673, 12350, 19908, 32127, 51887, 83848, 135550, 219193, 354517, 573462, 927708, 1500875, 2428263, 3928792, 6356682, 10285073, 16641325, 26925938, 43566772, 70492187, 114058403
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OFFSET
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1,1
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COMMENTS
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LINKS
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FORMULA
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Empirical: a(n) = 4*a(n-1) - 5*a(n-2) + a(n-3) + 2*a(n-4) - a(n-5) for n>6.
Empirical g.f.: x*(28 - 60*x + 10*x^2 + 45*x^3 - 25*x^4 + x^5) / ((1 - x)^3*(1 - x - x^2)). - Colin Barker, Aug 30 2018
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EXAMPLE
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Some solutions for n=3:
..1..0..0..0....1..1..0..0....1..1..0..1....1..0..0..0....1..0..1..0
..1..0..0..0....0..0..0..0....0..0..0..1....1..0..0..0....1..0..1..0
..0..0..0..0....0..0..0..0....0..0..0..1....0..0..0..0....1..0..1..0
..0..0..0..1....1..1..1..1....0..0..0..1....0..0..1..1....1..0..1..0
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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