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A231581
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Number of nX2 0..3 arrays with no element less than a strict majority of its horizontal, vertical, diagonal and antidiagonal neighbors
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1
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4, 28, 124, 602, 2776, 12922, 60720, 286047, 1335296, 6256326, 29377828, 137595239, 644951590, 3024402309, 14175895645, 66459189937, 311583082104, 1460702584712, 6848241858778, 32106603868468, 150524267596760, 705711781367756
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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) +6*a(n-2) +38*a(n-3) -161*a(n-4) -292*a(n-5) -953*a(n-6) +1185*a(n-7) +4928*a(n-8) +12336*a(n-9) +7076*a(n-10) -7076*a(n-11) -24464*a(n-12) -24608*a(n-13) -18624*a(n-14) -6720*a(n-15) -2304*a(n-16).
Empirical formula verified by Robert Israel, Dec 06 2017 (see link).
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EXAMPLE
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Some solutions for n=7
..0..0....3..0....2..1....0..3....2..0....2..3....2..2....1..1....3..3....0..0
..0..2....0..0....1..1....0..0....0..0....2..2....0..0....2..1....0..0....0..1
..1..0....0..0....0..0....0..1....1..0....3..2....0..0....1..2....0..0....0..0
..0..0....0..2....0..0....0..2....0..0....1..1....1..3....0..0....0..3....3..0
..2..0....0..1....0..2....0..0....0..1....1..1....0..0....0..0....0..0....0..1
..2..0....0..0....2..0....0..0....0..0....1..1....0..0....0..0....3..0....0..0
..0..0....0..0....0..0....2..0....3..0....2..1....2..3....0..2....0..0....0..3
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MAPLE
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rec:= a(n) = 4*a(n-1) +6*a(n-2) +38*a(n-3) -161*a(n-4) -292*a(n-5) -953*a(n-6) +1185*a(n-7) +4928*a(n-8) +12336*a(n-9) +7076*a(n-10) -7076*a(n-11) -24464*a(n-12) -24608*a(n-13) -18624*a(n-14) -6720*a(n-15) -2304*a(n-16):
Data := [4, 28, 124, 602, 2776, 12922, 60720, 286047, 1335296, 6256326, 29377828, 137595239, 644951590, 3024402309, 14175895645, 66459189937]:
f:= gfun:-rectoproc({rec, seq(a(i)=Data[i], i=1..16)}, a(n), remember):
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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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