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%I #7 Oct 01 2021 18:31:42
%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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