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A220612
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Number of ways to reciprocally link elements of an nX6 array either to themselves or to exactly two horizontal and vertical neighbors, without consecutive collinear links
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1
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1, 13, 43, 281, 1277, 7041, 34981, 183920, 937663, 4861869, 24977087, 128971605, 664092737, 3424806465, 17647051243, 90973240309, 468858278192, 2416753993341, 12456282450653, 64204249763017, 330924094972255, 1705685462529549
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OFFSET
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1,2
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COMMENTS
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LINKS
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FORMULA
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Empirical: a(n) = 3*a(n-1) +23*a(n-2) -40*a(n-3) -160*a(n-4) +190*a(n-5) +441*a(n-6) -369*a(n-7) -513*a(n-8) +278*a(n-9) +240*a(n-10) -64*a(n-11) -39*a(n-12) +3*a(n-13) +a(n-14)
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EXAMPLE
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Some solutions for n=3 0=self 2=n 4=w 6=e 8=s (reciprocal directions total 10)
.68.48.00.00.00.00...00.00.00.68.48.00...68.48.68.48.00.00...68.48.68.48.68.48
.26.24.00.00.68.48...00.00.00.26.24.00...26.24.26.24.68.48...26.24.26.24.26.24
.00.00.00.00.26.24...00.00.00.00.00.00...00.00.00.00.26.24...00.00.00.00.00.00
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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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