%N Number of isomers of polyhex hydrocarbons with C_(2v) symmetry with nineteen hexagons.
%C See Table 4 column 9 on page 615 of the paper by Caporossi and Hansen. Also the sequence starts for the hydrocarbon C_(54)H_(18).
%D G. Caporossi and P. Hansen, "Enumeration of Polyhex Hydrocarbons to h=21", J. Chem. Inf. Comput. Sci., vol. 38 (1998) pp. 610-619.
%e If the number of carbons is 56 then the number of isomers of polyhex hydrocarbons with C_(2v) symmetry with nineteen hexagons is 17 which is the third term in the sequence.
%Y Cf. A018190.
%A _Parthasarathy Nambi_, Aug 27 2006