A026298 Number of polyhexes of class PF2.

4, 28, 176, 950, 4908, 24402, 119240, 575348, 2757460, 13157752, 62638788, 297832008, 1415550920, 6728600060, 31998023632, 152271569872, 725231959452, 3457304575812, 16497751608120, 78804354881238, 376806016649964, 1803539487096138, 8641075826669256, 41441524062045660

Offset

7,1

Comments

See reference for precise definition.

Cyvin et al. has incorrect a(13) = 119204 and a(14) = 575312 due to using incorrect value for A039919(5); cf. A039659. - Sean A. Irvine, Sep 24 2019

Links

Table of n, a(n) for n=7..30.

S. J. Cyvin, Zhang Fuji, B. N. Cyvin, Guo Xiaofeng, and J. Brunvoll, Enumeration and classification of benzenoid systems. 32. Normal perifusenes with two internal vertices, J. Chem. Inform. Comput. Sci., 32 (1992), 532-540.

Formula

a(n + 4) = 3 * (N(n+2) - 6*N(n+1) + 8*N(n)) + A039919(floor((n+1)/2)) where N(n) = A002212(n) [from Cyvin]. - Sean A. Irvine, Sep 24 2019

Crossrefs

Cf. A026106, A026118, A030519, A030520, A030525, A030529, A030532, A030534, A002212, A039919.

Sequence in context: A272791 A291918 A223166 * A181895 A264707 A216211

Adjacent sequences: A026295 A026296 A026297 * A026299 A026300 A026301

Keyword

nonn

Author

N. J. A. Sloane.

Extensions

Corrected and extended by Sean A. Irvine, Sep 24 2019

Status

approved