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A205208
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Number of (n+1) X 2 0..2 arrays with the determinants of 2 X 2 subblocks nondecreasing rightwards and downwards.
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2
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81, 452, 1970, 8128, 33386, 139390, 588254, 2496440, 10620486, 45235186, 192770330, 821702110, 3502996038, 14934443890, 63672178746, 271466142110, 1157401680934, 4934619974706, 21038940313818, 89700376749918
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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) = 7*a(n-1) - 11*a(n-2) - 9*a(n-3) + 30*a(n-4) - 16*a(n-5) for n>13.
Empirical g.f.: x*(81 - 115*x - 303*x^2 + 39*x^3 - 202*x^4 + 562*x^5 + 1054*x^6 + 106*x^7 - 822*x^8 - 614*x^9 - 46*x^10 + 84*x^11 + 32*x^12) / ((1 - x)*(1 - 2*x)*(1 - 4*x - 3*x^2 + 8*x^3)). - Colin Barker, Mar 03 2018
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EXAMPLE
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Some solutions for n=4:
1 2 0 0 1 0 2 1 1 0 1 0 1 2 2 2 2 0 2 1
0 0 2 1 2 0 0 0 1 0 0 0 2 2 0 0 2 0 1 0
0 1 0 0 1 0 1 0 1 1 0 0 1 0 0 1 1 0 1 0
0 1 2 2 0 0 1 1 1 2 1 1 1 0 0 0 1 1 2 0
0 0 0 1 2 1 0 1 0 2 1 1 1 2 0 2 0 1 2 2
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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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