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%I A281690 #5 Jan 27 2017 12:36:34
%S A281690 0,6,847,19326,293814,3714629,42265965,449985840,4571830360,
%T A281690 44873281735,428836383879,4011945910730,36886705974618,
%U A281690 334269681986457,2992281836910513,26505969364372244,232662102182106796
%N A281690 Number of nX3 0..2 arrays with no element equal to more than one of its horizontal, diagonal or antidiagonal neighbors, with the exception of exactly two elements, and with new values introduced in order 0 sequentially upwards.
%C A281690 Column 3 of A281693.
%H A281690 R. H. Hardin, <a href="/A281690/b281690.txt">Table of n, a(n) for n = 1..210</a>
%F A281690 Empirical: a(n) = 21*a(n-1) -117*a(n-2) -155*a(n-3) +2070*a(n-4) +2406*a(n-5) -15836*a(n-6) -33948*a(n-7) +35640*a(n-8) +184600*a(n-9) +158208*a(n-10) -213408*a(n-11) -613504*a(n-12) -616320*a(n-13) -307200*a(n-14) -64000*a(n-15) for n>20
%e A281690 Some solutions for n=4
%e A281690 ..0..0..1. .0..0..1. .0..1..2. .0..1..1. .0..1..0. .0..0..1. .0..0..1
%e A281690 ..1..1..1. .2..1..1. .2..1..2. .0..0..0. .0..2..2. .2..2..2. .1..2..2
%e A281690 ..2..0..2. .2..2..0. .1..0..1. .0..1..2. .1..1..2. .1..0..1. .0..2..1
%e A281690 ..0..2..2. .0..1..0. .2..2..2. .0..1..1. .0..1..2. .2..2..2. .0..1..1
%Y A281690 Cf. A281693.
%K A281690 nonn
%O A281690 1,2
%A A281690 _R. H. Hardin_, Jan 27 2017

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