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A220559
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Number of ways to reciprocally link elements of an n X 5 array either to themselves or to exactly one horizontal or antidiagonal neighbor.
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1
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8, 149, 2604, 45966, 810778, 14298089, 252139015, 4446314533, 78407942556, 1382674335890, 24382584703194, 429971411669361, 7582273047532603, 133708574584054949, 2357865880743076540, 41579468847568886038
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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) = 21*a(n-1) - 62*a(n-2) + 47*a(n-3) - 5*a(n-4) for n>5.
Empirical g.f.: x*(8 - 19*x - 29*x^2 + 144*x^3 - 23*x^4) / ((1 - x)*(1 - 20*x + 42*x^2 - 5*x^3)). - Colin Barker, Jul 31 2018
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EXAMPLE
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Some solutions for n=3 0=self 3=ne 4=w 6=e 7=sw (reciprocal directions total 10):
..0..0..0..6..4....0..0..0..6..4....0..0..0..6..4....0..0..6..4..0
..6..4..0..6..4....0..6..4..0..0....0..6..4..7..0....0..7..7..7..0
..0..6..4..0..0....0..6..4..0..0....0..0..3..0..0....3..3..3..0..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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