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 A220727 Number of ways to reciprocally link elements of an 3Xn array either to themselves or to exactly two horizontal, diagonal or antidiagonal neighbors 1

%I

%S 1,4,30,230,1819,14466,114900,913187,7256380,57664692,458236178,

%T 3641435760,28937067889,229951848995,1827338913535,14521161884614,

%U 115394100670410,916992651769082,7286988782183320,57906904219355630

%N Number of ways to reciprocally link elements of an 3Xn array either to themselves or to exactly two horizontal, diagonal or antidiagonal neighbors

%C Row 3 of A220725

%H R. H. Hardin, <a href="/A220727/b220727.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = 5*a(n-1) +24*a(n-2) -a(n-3) -25*a(n-4) -33*a(n-5) +10*a(n-6) +19*a(n-7) +4*a(n-8) -4*a(n-9) -a(n-10)

%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 .69.49.00...00.69.47...00.67.47...69.47.00...00.79.00...00.67.47...00.69.47

%e .69.14.17...00.36.14...36.34.00...39.16.47...39.67.14...39.37.00...00.37.17

%e .00.13.00...00.00.00...00.00.00...00.13.00...36.14.00...36.14.00...36.34.00

%K nonn

%O 1,2

%A _R. H. Hardin_ Dec 18 2012

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Last modified November 27 04:52 EST 2021. Contains 349345 sequences. (Running on oeis4.)