cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-3 of 3 results.

A323930 Polycyclic aromatic hydrocarbons (for precise definition see He and He, 1986).

Original entry on oeis.org

1, 1, 3, 7, 22, 81, 331, 1436, 6510, 30129, 141512, 671538, 3210620, 15443871, 74662005, 362506902
Offset: 1

Views

Author

N. J. A. Sloane, Feb 09 2019

Keywords

References

  • N. Trinajstić, S. Nikolić, J. V. Knop, W. R. Müller and K. Szymanski, Computational Chemical Graph Theory: Characterization, Enumeration, and Generation of Chemical Structures by Computer Methods, Ellis Horwood, 1991. [incorrectly gives a(12) = 671512 in Table 4.13]

Crossrefs

A018190 is a very similar sequence with (as He and He remark) a slightly different definition. Cf. A000228, A038147.

Formula

a(n) = A018190(n) + A038140(n) + A038141(n). - Andrey Zabolotskiy, Feb 16 2023

Extensions

a(10)-a(16) from Cyvin, Brunvoll & Cyvin (Table 1) added by Andrey Zabolotskiy, Feb 08 2023

A038141 Number of planar polyhexes with n cells with at least two holes, all holes having size at least two.

Original entry on oeis.org

0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 11, 149, 1618, 15123, 125764
Offset: 1

Views

Author

Keywords

Comments

Planar, proper multiple coronoid systems enumerated by area. Free systems are enumerated, i.e., translations, rotations and reflections are regarded as the same configuration.
The last term includes 4 polyhexes with three holes.

References

  • S. J. Cyvin, J. Brunvoll, R. S. Chen, B. N. Cyvin, F. J. Zhang, Theory of Coronoid Hydrocarbons II, Lecture Notes in Chemistry 62, Springer-Verlag, 1994. (see table 3.2, p. 66)

Crossrefs

Cf. A018190.
Cf. A000228 (hexagonal free polyominoes), A038140 (planar single coronoids).

Extensions

Edited by Markus Voege (markus.voege(AT)inria.fr), Dec 03 2003

A122671 Number of catacondensed coronoid systems with n hexagons with a single hole.

Original entry on oeis.org

1, 3, 15, 62, 312, 1435, 6785
Offset: 8

Views

Author

N. J. A. Sloane, Sep 23 2006

Keywords

Crossrefs

Cf. A038140.

Extensions

Name clarified by Andrey Zabolotskiy, Feb 16 2023
Showing 1-3 of 3 results.