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 #8 Feb 07 2019 08:42:07
%S 0,2,3,10,27,76,214,599,1683,4721,13250,37183,104346,292828,821761,
%T 2306111,6471639,18161366,50966255,143026636,401375754,1126381063,
%U 3160963987,8870615501,24893614638,69858968603,196045273658,550161991984
%N Number of n X 2 0..1 arrays with every element both equal and not equal to some elements at offset (-1,0) (-1,1) (0,-1) (0,1) or (1,0), with upper left element zero.
%H R. H. Hardin, <a href="/A278088/b278088.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = a(n-1) + 4*a(n-2) + 3*a(n-3) for n>5.
%F Empirical g.f.: x^2*(2 + x - x^2 - x^3) / (1 - x - 4*x^2 - 3*x^3). - _Colin Barker_, Feb 07 2019
%e All solutions for n=4:
%e ..0..1. .0..0. .0..0. .0..1. .0..1. .0..1. .0..0. .0..1. .0..0. .0..0
%e ..0..1. .1..1. .1..1. .0..1. .0..1. .0..1. .1..1. .0..1. .1..1. .1..1
%e ..1..1. .0..1. .1..0. .0..1. .0..1. .0..0. .1..1. .1..0. .0..0. .0..1
%e ..0..0. .0..0. .1..0. .0..1. .0..0. .1..1. .0..0. .1..0. .1..1. .0..1
%Y Column 2 of A278094.
%K nonn
%O 1,2
%A _R. H. Hardin_, Nov 11 2016