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A003104 Number of hexagonal n-element polyominoes whose graph is a path.
(Formerly M1208)
10
1, 1, 2, 4, 10, 24, 67, 182, 520, 1474, 4248, 12196, 35168, 101226, 291565, 838764, 2412033, 6929754, 19896915 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

In other words, number of 2-sided strip polyhexes with n cells.

REFERENCES

E. M. Palmer, Variations of the cell growth problem, Lect. Notes Math. 303 (1972), 215-224.

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

LINKS

Table of n, a(n) for n=1..19.

A. T. Balaban, J. Brunvoll, B. N. Cyvin & S. J. Cyvin, Enumeration of branched catacondensed benzenoid hydrocarbons and their numbers of Kekulé structures Tetrahedron, 44(1) (1988), 221-228. See Table 1.

Wenchen He and Wenjie He, Generation and enumeration of planar polycyclic aromatic hydrocarbons, Tetrahedron 42.19 (1986): 5291-5299. See Table 1, column B.

Ed Pegg, Jr., Illustrations of polyforms

Eric Weisstein's World of Mathematics, Polyhex

CROSSREFS

Sequence in context: A000084 A057734 A151516 * A121186 A028506 A148088

Adjacent sequences:  A003101 A003102 A003103 * A003105 A003106 A003107

KEYWORD

nonn,more,changed

AUTHOR

N. J. A. Sloane.

EXTENSIONS

a(8)-a(12) from Ed Pegg Jr, May 13 2009

a(13)-a(19) from Joseph Myers, Nov 26 2010

STATUS

approved

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Last modified February 17 11:57 EST 2019. Contains 320219 sequences. (Running on oeis4.)