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 A220734 Number of ways to reciprocally link elements of an nX4 array either to themselves or to exactly two horizontal, diagonal and antidiagonal neighbors, without consecutive collinear links 1
 1, 13, 103, 712, 5760, 45421, 355883, 2807273, 22112517, 174154372, 1371967416, 10807412577, 85133340257, 670628304993, 5282781003159, 41614380864876, 327811678257588, 2582291933091677, 20341654064411427, 160238619700892677 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Column 4 of A220738 LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = 9*a(n-1) -4*a(n-2) -23*a(n-3) -153*a(n-4) +204*a(n-5) +564*a(n-6) -700*a(n-7) +95*a(n-8) +2061*a(n-9) -3000*a(n-10) -4459*a(n-11) +2151*a(n-12) +5800*a(n-13) +320*a(n-14) -1276*a(n-15) -925*a(n-16) +233*a(n-17) +48*a(n-18) +13*a(n-19) -a(n-20) EXAMPLE Some solutions for n=3 0=self 1=nw 3=ne 4=w 6=e 7=sw 9=se (reciprocal directions total 10) .00.69.49.00...00.69.49.00...00.69.47.00...00.67.49.00...69.47.00.00 .00.00.17.17...69.47.16.14...00.39.16.47...36.47.67.14...39.16.47.00 .00.36.34.00...36.14.00.00...00.00.13.00...36.34.00.00...00.13.00.00 CROSSREFS Sequence in context: A119594 A066034 A228213 * A268991 A216179 A240804 Adjacent sequences:  A220731 A220732 A220733 * A220735 A220736 A220737 KEYWORD nonn AUTHOR R. H. Hardin Dec 18 2012 STATUS approved

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Last modified September 16 18:26 EDT 2021. Contains 347473 sequences. (Running on oeis4.)