cp's OEIS Frontend

A183325 Number of n X 4 binary arrays with each 1 adjacent to exactly two other 1s.

%I A183325 #8 Mar 27 2018 08:49:44
%S A183325 1,4,10,27,72,179,447,1139,2912,7434,18949,48256,122905,313153,797993,
%T A183325 2033404,5181138,13201355,33636776,85706587,218381247,556436971,
%U A183325 1417803304,3612566114,9204828661,23453934912,59760710321,152270499073
%N A183325 Number of n X 4 binary arrays with each 1 adjacent to exactly two other 1s.
%C A183325 Column 4 of A183328.
%H A183325 R. H. Hardin, <a href="/A183325/b183325.txt">Table of n, a(n) for n = 1..200</a>
%F A183325 Empirical: a(n) = 3*a(n-1) - 2*a(n-2) + 2*a(n-3) + 2*a(n-5) - 5*a(n-7) - 3*a(n-8).
%F A183325 Empirical g.f.: x*(1 + x)^2*(1 - x + x^2 + 2*x^3 - 2*x^4 - 3*x^5) / (1 - 3*x + 2*x^2 - 2*x^3 - 2*x^5 + 5*x^7 + 3*x^8). - _Colin Barker_, Mar 27 2018
%e A183325 Some solutions for 8 X 4:
%e A183325 ..1..1..1..1....1..1..1..1....0..0..0..0....1..1..1..0....0..1..1..0
%e A183325 ..1..0..0..1....1..0..0..1....0..0..0..0....1..0..1..1....0..1..1..0
%e A183325 ..1..1..0..1....1..0..1..1....0..0..1..1....1..0..0..1....0..0..0..0
%e A183325 ..0..1..0..1....1..0..1..0....0..0..1..1....1..0..0..1....0..1..1..1
%e A183325 ..0..1..0..1....1..0..1..1....0..0..0..0....1..0..0..1....0..1..0..1
%e A183325 ..0..1..1..1....1..0..0..1....0..0..1..1....1..0..0..1....1..1..0..1
%e A183325 ..0..0..0..0....1..0..0..1....0..0..1..1....1..1..1..1....1..0..0..1
%e A183325 ..0..0..0..0....1..1..1..1....0..0..0..0....0..0..0..0....1..1..1..1
%Y A183325 Cf. A183328.
%K A183325 nonn
%O A183325 1,2
%A A183325 _R. H. Hardin_, Jan 03 2011