

A038142


Number of planar catapolyhexes with n cells.


6



1, 1, 2, 5, 12, 36, 118, 411, 1489, 5572, 21115
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OFFSET

1,3


COMMENTS

Number of catacondensed benzenoid hydrocarbons with n hexagons.
a(n) is the number of ncelled polyhexes with perimeter 4n+2. 4n+2 is the maximal perimeter of an ncelled polyhex. a(n) is the number of ncelled polyhexes that have a tree as their connectedness graph (vertices of this graph correspond to cells and two vertices are connected if the corresponding cells have a common edge)  Tanya Khovanova, Jul 27 2007


LINKS

Table of n, a(n) for n=1..11.
Andrew Clarke, Isoperimetrical Polyhexes
Wenchen He and Wenjie He, Generation and enumeration of planar polycyclic aromatic hydrocarbons, Tetrahedron 42.19 (1986): 52915299. See Table 3.
J. V. Knop et al., On the total number of polyhexes, Match, No. 16 (1984), 119134.
N. Trinajstich, Z. Jerievi, J. V. Knop, W. R. Muller and K. Szymanski, Computer Generation of Isomeric Structures, Pure & Appl. Chem., Vol. 55, No. 2, pp. 379390, 1983.
Eric Weisstein's World of Mathematics, Polyhex.
Eric Weisstein's World of Mathematics, Fusene


CROSSREFS

Cf. A018190, A038143.
a(n) <= A000228(n), a(n) <= A057779(2n+1).
Sequence in context: A197444 A094717 A323933 * A287427 A267397 A267398
Adjacent sequences: A038139 A038140 A038141 * A038143 A038144 A038145


KEYWORD

nonn,hard,more


AUTHOR

N. J. A. Sloane.


EXTENSIONS

a(11) from Tanya Khovanova, Jul 27 2007


STATUS

approved



