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A220711
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Number of ways to reciprocally link elements of an 6Xn array either to themselves or to exactly two horizontal and antidiagonal neighbors, without consecutive collinear links
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1
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1, 1, 13, 60, 317, 1617, 8338, 42873, 221082, 1139020, 5870960, 30259204, 155962396, 803874071, 4143371101, 21356146495, 110075467413, 567360680620, 2924337273221, 15072870834560, 77689863937436, 400435729023800
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OFFSET
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1,3
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COMMENTS
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LINKS
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FORMULA
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Empirical: a(n) = a(n-1) +33*a(n-2) -a(n-3) -351*a(n-4) -75*a(n-5) +1760*a(n-6) +436*a(n-7) -4708*a(n-8) -997*a(n-9) +6997*a(n-10) +1085*a(n-11) -5748*a(n-12) -564*a(n-13) +2512*a(n-14) +131*a(n-15) -543*a(n-16) -7*a(n-17) +49*a(n-18) -a(n-19) -a(n-20) for n>24
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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)
.00.67.47...00.00.00...00.00.00...00.00.00...00.67.47...00.00.00...00.00.00
.36.34.00...00.67.47...00.00.00...00.00.00...36.34.00...00.67.47...00.00.00
.00.00.00...36.34.00...00.00.00...00.00.00...00.67.47...36.34.00...00.67.47
.00.67.47...00.67.47...00.00.00...00.00.00...36.34.00...00.00.00...36.34.00
.36.34.00...36.34.00...00.00.00...00.67.47...00.00.00...00.00.00...00.00.00
.00.00.00...00.00.00...00.00.00...36.34.00...00.00.00...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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