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%I #6 Mar 10 2023 13:36:51
%S 21,5536,940432,174911750,32001129185,5873481159019,1077372801893440,
%T 197644957649145164,36257360400073221806,6651328207323063530996,
%U 1220169722761405665767328,223837152224277574339972896
%N Number of ways to reciprocally link elements of an n X 7 array either to themselves or to exactly one horizontal, vertical or antidiagonal neighbor.
%C Column 7 of A220553.
%H R. H. Hardin, <a href="/A220552/b220552.txt">Table of n, a(n) for n = 1..210</a>
%e Some solutions for n=3 0=self 2=n 3=ne 4=w 6=e 7=sw 8=s (reciprocal directions total 10)
%e ..0..7..7..7..0..0..0....0..7..8..8..0..6..4....0..7..7..6..4..6..4
%e ..3..3..3..7..7..7..0....3..0..2..2..0..0..7....3..3..7..0..6..4..0
%e ..0..0..3..3..3..0..0....0..6..4..0..0..3..0....0..3..0..0..6..4..0
%Y Cf. A220553.
%K nonn
%O 1,1
%A _R. H. Hardin_, Dec 15 2012
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