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%I #4 Dec 16 2012 17:53:26
%S 1,155,6156,308246,14637699,702811381,33667621356,1613595307718,
%T 77327320807492,3705787367955871,177593105803460322,
%U 8510833856676985632,407866501681469579790,19546273938797565641009,936720274971414734673655
%N Number of ways to reciprocally link elements of an nX4 array either to themselves or to exactly two king-move neighbors
%C Column 4 of A220595
%H R. H. Hardin, <a href="/A220592/b220592.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 40*a(n-1) +395*a(n-2) -769*a(n-3) +2095*a(n-4) -16049*a(n-5) -71697*a(n-6) -119950*a(n-7) +1037497*a(n-8) -139363*a(n-9) -1979661*a(n-10) +1507756*a(n-11) +1041993*a(n-12) -2247051*a(n-13) +1215317*a(n-14) -16637*a(n-15) -311055*a(n-16) +67983*a(n-17) +54951*a(n-18) -4355*a(n-19) -9884*a(n-20) +766*a(n-21) +683*a(n-22) -103*a(n-23) -9*a(n-24) +2*a(n-25)
%e 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)
%e .00.68.47.00...69.47.89.00...69.46.46.48...89.67.48.00...00.67.46.47
%e .89.23.69.47...36.14.26.14...00.18.78.28...23.17.28.00...39.67.34.78
%e .26.14.36.14...00.00.00.00...00.23.26.24...36.46.24.00...36.14.36.24
%K nonn
%O 1,2
%A _R. H. Hardin_ Dec 16 2012
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