%I #3 Mar 30 2012 16:50:30
%S 1,3,21,116,692,3776,20216,104448
%N Numbers of isomers of unbranched a-4-catapolyheptagons - see Brunvoll reference for precise definition.
%D J. Brunvoll, S. J. Cyvin and B. N. Cyvin, Isomer enumeration of polygonal systems..., J. Molec. Struct. (Theochem), 364 (1996), 1-13.
%K nonn
%O 3,2
%A _N. J. A. Sloane_, Aug 13 2006