OFFSET
0,5
LINKS
S. J. Cyvin et al., Enumeration and Classification of Certain Polygonal Systems Representing Polycyclic Conjugated Hydrocarbons: Annelated Catafusenes, J. Chem. Inform. Comput. Sci., 34 (1994), 1174-1180.
F. Harary and R. C. Read, The enumeration of tree-like polyhexes, Proc. Edinburgh Math. Soc. (2) 17 (1970), 1-13.
FORMULA
G.f.: (1/2)*U(z^2)*V(z) + (1/6)*U(z)^3 + (1/3)*U(z^3) where U(z) = (1 - 3z - sqrt(1 - 6z + 5z^2))/(2z) and V(z) = (1 - z^2 - sqrt(1 - 6z^2 + 5z^4))/(2*z*(1-z)) (eq. (26) in the Cyvin et al. paper).
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
More terms from Emeric Deutsch, Mar 14 2004
STATUS
approved