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A038142 Number of planar cata-polyhexes with n cells. 6
1, 1, 2, 5, 12, 36, 118, 411, 1489, 5572, 21115 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Number of cata-condensed benzenoid hydrocarbons with n hexagons.

a(n) is the number of n-celled polyhexes with perimeter 4n+2. 4n+2 is the maximal perimeter of an n-celled polyhex. a(n) is the number of n-celled 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): 5291-5299. See Table 3.

J. V. Knop et al., On the total number of polyhexes, Match, No. 16 (1984), 119-134.

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. 379-390, 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

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Last modified August 26 00:35 EDT 2019. Contains 326324 sequences. (Running on oeis4.)