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A220643 Number of ways to reciprocally link elements of an n X 7 array either to themselves or to exactly one king-move neighbor.

%I A220643 #10 Nov 03 2023 15:24:43
%S A220643 1,21,13152,3725843,1299348473,431408410784,145000880411157,
%T A220643 48590896359378961,16295162098717276928,5463664833842177843423,
%U A220643 1832013557267266441097285,614283122531442244792501056,205972692517470174457341794041,69063792561944299889152684046621
%N A220643 Number of ways to reciprocally link elements of an n X 7 array either to themselves or to exactly one king-move neighbor.
%H A220643 Alois P. Heinz, <a href="/A220643/b220643.txt">Table of n, a(n) for n = 0..200</a> (terms n = 1..135 from R. H. Hardin)
%e A220643 Some solutions for n=3 0=self 1=nw 2=n 3=ne 4=w 6=e 7=sw 8=s 9=se (reciprocal directions total 10)
%e A220643 ..0..0..0..0..0..7..0....0..0..9..6..4..0..0....0..6..4..0..0..7..0
%e A220643 ..6..4..7..9..3..8..0....6..4..9..1..0..7..0....6..4..8..9..3..6..4
%e A220643 ..0..3..0..0..1..2..0....0..0..0..1..3..6..4....0..0..2..0..1..0..0
%Y A220643 Column 7 of A220644.
%K A220643 nonn
%O A220643 0,2
%A A220643 _R. H. Hardin_, Dec 17 2012