Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #9 Feb 27 2018 07:11:06
%S 1,9,18,30,107,265,553,1505,3852,8922,22477,56889,137617,340401,
%T 851098,2091618,5160851,12817517,31655009,78159377,193558964,
%U 478614470,1182673261,2925763109,7235864705,17887850273,44237338898,109401520982
%N Number of n X 3 binary arrays with every 1 having exactly two king-move neighbors equal to 1.
%C Column 3 of A183450.
%H R. H. Hardin, <a href="/A183444/b183444.txt">Table of n, a(n) for n = 1..200</a>
%F Empirical: a(n) = 2*a(n-1) - a(n-2) + 8*a(n-3) - 7*a(n-4) + 2*a(n-5) - 2*a(n-6).
%F Empirical g.f.: x*(1 + 7*x + x^2 - 5*x^3 - 2*x^5) / (1 - 2*x + x^2 - 8*x^3 + 7*x^4 - 2*x^5 + 2*x^6). - _Colin Barker_, Feb 27 2018
%e Some solutions for 5 X 3:
%e ..0..1..0....1..1..0....0..0..0....0..0..0....1..1..0....0..0..0....0..0..1
%e ..0..1..1....1..0..0....0..1..1....0..1..0....0..1..0....0..0..0....0..1..1
%e ..0..0..0....0..0..0....0..0..1....1..0..1....0..0..0....0..0..0....0..0..0
%e ..0..1..0....0..1..1....1..0..0....1..0..1....1..0..0....1..1..0....1..0..0
%e ..1..1..0....0..0..1....1..1..0....0..1..0....1..1..0....1..0..0....1..1..0
%Y Cf. A183450.
%K nonn
%O 1,2
%A _R. H. Hardin_, Jan 04 2011