%I
%S 1,2,5,14,38,102,273,731,1958,5245,14050,37636,100816,270057,723405,
%T 1937794,5190793,13904642,37246538,99772766,267262553,715919535,
%U 1917742590,5137081001,13760762966,36861127432,98740361920,264497039329
%N Length of lists created by n substitutions k > Range[0,Mod[k+1,4]] starting with {0}.
%C equivalent to replacements 0>{0,1}; 1>{0,1,2}; 2>{0,1,2,3}; 3>{0} operating n times with {0}.
%F G.f.: (1x+x^3)/(x^21+3 x+x^4))
%e {0}, {0,1}, {0,1,0,1,2}, {0,1,0,1,2,0,1,0,1,2,0,1,2,3} have lengths 1, 2, 5, 14.
%t Length/@Flatten/@NestList[ # /. k_Integer:>Range[0, Mod[k+1, 4]]&, {0}, 8]
%K nonn
%O 0,2
%A _Wouter Meeussen_, May 11 2003
