%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(n1)  8*a(n3)  4*a(n4) 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
