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 A220707 Number of ways to reciprocally link elements of an n X 7 array either to themselves or to exactly two horizontal and antidiagonal neighbors, without consecutive collinear links. 1

%I

%S 1,13,48,298,1520,8338,44976,244029,1322551,7171769,38885648,

%T 210854845,1143330649,6199601829,33616711696,182283373322,

%U 988413912488,5359579124490,29061800830768,157584813722329,854488462716575

%N Number of ways to reciprocally link elements of an n X 7 array either to themselves or to exactly two horizontal and antidiagonal neighbors, without consecutive collinear links.

%C Column 7 of A220708.

%H R. H. Hardin, <a href="/A220707/b220707.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = 5*a(n-1) +6*a(n-2) -17*a(n-3) -19*a(n-4) +10*a(n-5) +16*a(n-6) -46*a(n-7) +7*a(n-8) +15*a(n-9) -14*a(n-10) +21*a(n-11) +3*a(n-12) +10*a(n-13) +8*a(n-14) +2*a(n-15) +5*a(n-16) +a(n-17) +2*a(n-18) -a(n-19) -a(n-20).

%e Some solutions for n=3 0=self 3=ne 4=w 6=e 7=sw (reciprocal directions total 10)

%e .00.00.00.00.00.00.00...00.00.00.00.00.00.00...00.67.47.00.00.00.00

%e .00.00.67.47.00.00.00...00.00.67.47.67.47.00...36.34.00.00.00.67.47

%e .00.36.34.00.00.00.00...00.36.34.36.34.00.00...00.00.00.00.36.34.00

%Y Cf. A220708.

%K nonn

%O 1,2

%A _R. H. Hardin_, Dec 18 2012

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Last modified March 20 22:57 EDT 2023. Contains 361392 sequences. (Running on oeis4.)