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Number of 3Xn 0..1 arrays with every element equal to 0, 1 or 3 horizontally, diagonally or antidiagonally adjacent elements, with upper left element zero.
1

%I #4 Apr 02 2018 14:50:47

%S 4,6,7,12,20,34,56,94,156,262,436,730,1216,2034,3392,5670,9460,15806,

%T 26380,44066,73560,122858,205112,342542,571916,955062,1594660,2662890,

%U 4446320,7424674,12397424,20701558,34566948,57720430,96380668,160937266

%N Number of 3Xn 0..1 arrays with every element equal to 0, 1 or 3 horizontally, diagonally or antidiagonally adjacent elements, with upper left element zero.

%C Row 3 of A302163.

%H R. H. Hardin, <a href="/A302165/b302165.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = a(n-1) +a(n-2) -a(n-3) +2*a(n-4) for n>6

%e Some solutions for n=5

%e ..0..0..1..0..1. .0..0..1..1..0. .0..1..0..1..0. .0..1..0..1..0

%e ..0..1..0..0..1. .0..1..0..1..0. .0..1..0..1..1. .1..1..0..1..1

%e ..0..1..0..1..0. .0..1..0..1..0. .0..1..0..1..0. .0..1..0..1..0

%Y Cf. A302163.

%K nonn

%O 1,1

%A _R. H. Hardin_, Apr 02 2018