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A206931
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Number of n X 3 0..1 arrays avoiding 0 0 0 horizontally and 0 1 1 vertically.
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1
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7, 49, 211, 811, 2791, 9055, 28081, 84403, 247705, 713857, 2027929, 5695201, 15845455, 43747201, 120004363, 327401947, 889103743, 2404885423, 6482464537, 17421401395, 46696588561, 124877198881, 333267920209, 887801858209
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OFFSET
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1,1
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COMMENTS
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Column 3 of A206936.
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LINKS
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R. H. Hardin, Table of n, a(n) for n = 1..210
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FORMULA
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Empirical: a(n) = 6*a(n-1) - 9*a(n-2) - 6*a(n-3) + 18*a(n-4) - 9*a(n-6) + a(n-8).
Empirical g.f.: x*(7 + 7*x - 20*x^2 + 28*x^3 - 8*x^4 - 8*x^5 + x^6 + x^7) / ((1 - x)*(1 + x)*(1 - 3*x + x^2)*(1 - x - x^2)*(1 - 2*x - x^2)). - Colin Barker, Jun 17 2018
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EXAMPLE
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Some solutions for n=4:
0 0 1 0 1 0 0 0 1 1 1 1 0 0 1 1 1 0 1 1 0
0 1 1 1 0 1 0 0 1 1 1 1 0 1 1 1 0 1 0 0 1
1 0 0 0 1 0 1 0 1 1 1 1 0 0 1 1 0 0 1 1 0
0 0 1 1 0 0 0 0 1 1 1 1 0 1 0 0 1 1 0 0 1
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CROSSREFS
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Cf. A206936.
Sequence in context: A221962 A294292 A015953 * A188608 A188601 A206866
Adjacent sequences: A206928 A206929 A206930 * A206932 A206933 A206934
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KEYWORD
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nonn
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AUTHOR
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R. H. Hardin, Feb 13 2012
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STATUS
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approved
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