G. Brinkmann, G. Caporossi and P. Hansen, "A survey and new results on computer enumeration of polyhex and fusene hydrocarbons", J. Chem. Inf. Comput. Sci., vol. 43 (2003) pp. 842-851. See Table 4 column 4 on page 846.
Table of n, a(n) for n=61..69.
If n=61 then the number of benzenoids with 21 hexagons with C_(3h) symmetry is 2.
If n=64 then the number of benzenoids with 21 hexagons with C_(3h) symmetry is 4.
Cf. A122539, A121964.
Sequence in context: A102049 A058522 A292534 * A296276 A092458 A071779
Adjacent sequences: A122733 A122734 A122735 * A122737 A122738 A122739
Parthasarathy Nambi, Sep 24 2006