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%I #7 Feb 18 2018 10:02:42
%S 0,1,7,38,190,918,4367,20623,97052,455960,2140404,10043697,47120343,
%T 221046178,1036902766,4863888050,22815211759,107019570351,
%U 501996648392,2354712588592,11045229346424,51809744028497,243023401329015
%N Number of n X 2 arrays of occupancy after each element moves to some horizontal or vertical neighbor but without 2-loops
%C Column 2 of A217346.
%H R. H. Hardin, <a href="/A217340/b217340.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 7*a(n-1) -11*a(n-2) +a(n-3) -a(n-4).
%F Empirical g.f.: x^2 / (1 - 7*x + 11*x^2 - x^3 + x^4). - _Colin Barker_, Feb 18 2018
%e All solutions for n=3:
%e ..0..0....1..1....1..1....1..1....1..0....0..1....1..1
%e ..2..2....1..2....2..1....2..2....2..1....1..2....1..1
%e ..1..1....0..1....1..0....0..0....1..1....1..1....1..1
%K nonn
%O 1,3
%A _R. H. Hardin_, Oct 01 2012