%I #16 Feb 22 2021 15:44:05
%S 4,7,25,109,514,2641,14354,81325,475936,2854145
%N Number of distinct finite languages over binary alphabet, whose minimum regular expression has reverse Polish length 2n-1.
%H Hermann Gruber, Jonathan Lee, and Jeffrey Shallit, <a href="http://arxiv.org/abs/1204.4982">Enumerating regular expressions and their languages</a>, arXiv:1204.4982v1 [cs.FL], 2012.
%K nonn,hard
%O 1,1
%A _Hermann Gruber_, Apr 26 2012