function out =fib(n)
% out1 generates all strings with no successive 1's
if n==0
    out = {};
elseif n==1
    out ={'0', '1'};
else 
    out4 = fib(n-1); 
    out2 = filter_out(out4,'0');
    out3 = filter_out(out4, '1');
    out = [concat(out2, '0'), concat(out2,'1')];
    out = [out, concat(out3,'0')];
end;
    
 