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 A220561 Number of ways to reciprocally link elements of an nX7 array either to themselves or to exactly one horizontal or antidiagonal neighbor 1
 21, 1544, 101052, 6743873, 449429440, 29955561052, 1996515036228, 133064181801048, 8868465829053416, 591065515195237024, 39393331961841054032, 2625486595153945514656, 174983417444316851450400 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Column 7 of A220562 LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = 85*a(n-1) -1330*a(n-2) +7350*a(n-3) -15316*a(n-4) +12720*a(n-5) -3168*a(n-6) for n>9 EXAMPLE Some solutions for n=3 0=self 3=ne 4=w 6=e 7=sw (reciprocal directions total 10) ..0..0..0..0..0..7..0....0..0..0..0..7..6..4....0..0..0..0..0..6..4 ..0..6..4..0..3..6..4....6..4..7..3..0..0..0....6..4..6..4..6..4..0 ..6..4..6..4..0..0..0....0..3..0..6..4..0..0....6..4..0..0..6..4..0 CROSSREFS Sequence in context: A035319 A278323 A301432 * A239267 A258305 A081786 Adjacent sequences: A220558 A220559 A220560 * A220562 A220563 A220564 KEYWORD nonn AUTHOR R. H. Hardin Dec 16 2012 STATUS approved

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Last modified March 1 20:05 EST 2024. Contains 370443 sequences. (Running on oeis4.)