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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

%I

%S 1,13,103,712,5760,45421,355883,2807273,22112517,174154372,1371967416,

%T 10807412577,85133340257,670628304993,5282781003159,41614380864876,

%U 327811678257588,2582291933091677,20341654064411427,160238619700892677

%N 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

%C Column 4 of A220738

%H R. H. Hardin, <a href="/A220734/b220734.txt">Table of n, a(n) for n = 1..210</a>

%F 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)

%e Some solutions for n=3 0=self 1=nw 3=ne 4=w 6=e 7=sw 9=se (reciprocal directions total 10)

%e .00.69.49.00...00.69.49.00...00.69.47.00...00.67.49.00...69.47.00.00

%e .00.00.17.17...69.47.16.14...00.39.16.47...36.47.67.14...39.16.47.00

%e .00.36.34.00...36.14.00.00...00.00.13.00...36.34.00.00...00.13.00.00

%K nonn

%O 1,2

%A _R. H. Hardin_ Dec 18 2012

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Last modified October 17 17:21 EDT 2021. Contains 348065 sequences. (Running on oeis4.)