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%I #6 Mar 07 2022 14:40:02
%S 2,5,7,17,35,61,127,265,507,1013,2071,4097,8147,16429,32815,65401,
%T 131115,262373,523975,1048433,2097923,4193821,8387551,16779241,
%U 33554523,67104725,134221687,268439777,536858675,1073745421,2147504527,4294939225
%N Number of n X 2 0..1 arrays with every element unequal to 0, 1, 3 or 4 king-move adjacent elements, with upper left element zero.
%C Column 2 of A303808.
%H R. H. Hardin, <a href="/A303802/b303802.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 2*a(n-1) -a(n-2) +4*a(n-3) -4*a(n-4) for n>5.
%e Some solutions for n=5
%e ..0..1. .0..0. .0..0. .0..1. .0..0. .0..0. .0..1. .0..0. .0..1. .0..0
%e ..0..0. .0..0. .0..0. .1..1. .0..1. .0..1. .0..0. .0..1. .1..1. .1..0
%e ..1..1. .0..0. .1..0. .0..0. .1..1. .1..1. .0..0. .1..1. .0..0. .1..1
%e ..0..0. .0..0. .1..1. .1..0. .1..1. .1..1. .0..0. .1..1. .1..1. .1..1
%e ..1..0. .0..0. .1..1. .1..1. .1..1. .1..0. .0..1. .0..1. .1..0. .1..0
%Y Cf. A303808.
%K nonn
%O 1,1
%A _R. H. Hardin_, Apr 30 2018
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