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 19 2018 11:01:52
%S 0,0,1,2,8,28,94,304,960,2976,9096,27488,82304,244544,721888,2119168,
%T 6191104,18011136,52203648,150809088,434382848,1247857664,3576143360,
%U 10226274304,29184704512,83138240512,236438194176,671370043392
%N Number of n X 1 0..2 arrays with no element equal to more than one of its horizontal and vertical neighbors, with the exception of exactly one element, and with new values introduced in order 0 sequentially upwards.
%C Column 1 of A280284.
%H R. H. Hardin, <a href="/A280279/b280279.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 4*a(n-1) - 8*a(n-3) - 4*a(n-4) for n>7.
%F Empirical g.f.: x^3*(1 - 2*x + 4*x^3 + 2*x^4) / (1 - 2*x - 2*x^2)^2. - _Colin Barker_, Feb 19 2018
%e All solutions for n=4:
%e ..0. .0
%e ..1. .0
%e ..1. .0
%e ..1. .1
%Y Cf. A280284.
%K nonn
%O 1,4
%A _R. H. Hardin_, Dec 30 2016