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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. 2
 1, 21, 13152, 3725843, 1299348473, 431408410784, 145000880411157, 48590896359378961, 16295162098717276928, 5463664833842177843423, 1832013557267266441097285, 614283122531442244792501056, 205972692517470174457341794041, 69063792561944299889152684046621 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Alois P. Heinz, Table of n, a(n) for n = 0..200 (terms n = 1..135 from R. H. Hardin) EXAMPLE 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) ..0..0..0..0..0..7..0....0..0..9..6..4..0..0....0..6..4..0..0..7..0 ..6..4..7..9..3..8..0....6..4..9..1..0..7..0....6..4..8..9..3..6..4 ..0..3..0..0..1..2..0....0..0..0..1..3..6..4....0..0..2..0..1..0..0 CROSSREFS Column 7 of A220644. Sequence in context: A203674 A250065 A180769 * A185557 A276513 A167063 Adjacent sequences: A220640 A220641 A220642 * A220644 A220645 A220646 KEYWORD nonn AUTHOR R. H. Hardin, Dec 17 2012 STATUS approved

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Last modified December 7 10:56 EST 2023. Contains 367650 sequences. (Running on oeis4.)