%I #5 Mar 30 2013 04:52:22
%S 1,0,3,9,42,182,821,3754
%N Sequence a_{a_n} arising in enumeration of arrays of directed blocks (see Quaintance reference for precise definition), where a_n is A129878.
%D Jocelyn Quaintance, Combinatoric Enumeration of Two-Dimensional Proper Arrays, Discrete Math., 307 (2007), 1844-1864.
%F See Quaintance reference for generating functions that produce A129872-A129886.
%K nonn,more
%O 1,3
%A _N. J. A. Sloane_, May 26 2007