A110696 Kekulé numbers for certain benzenoids of trigonal symmetry.

1, 28, 1456, 66178, 3014128, 143076778, 7087202890, 363641489638, 19183237689328, 1034361829223578, 56758935931548706, 3159417013205183638, 177966175592478108106, 10125526670502832205398, 581051793331857091649398

Offset

0,2

References

S. J. Cyvin and I. Gutman, Kekulé structures in benzenoid hydrocarbons, Lecture Notes in Chemistry, No. 46, Springer, New York, 1988 (see p. 313).

Links

G. C. Greubel, Table of n, a(n) for n = 0..550

Formula

a(n) = 9*binomial(2n, n)^3 - 15*binomial(2n, n)^2 + 9*binomial(2n, n) - 2.

Maple

a:=n->9*binomial(2*n, n)^3-15*binomial(2*n, n)^2+9*binomial(2*n, n)-2; seq(a(n), n=0..16);

Mathematica

Table[9*Binomial[2*n, n]^3 - 15*Binomial[2*n, n]^2 + 9*Binomial[2*n, n] - 2, {n, 0, 50}] (* G. C. Greubel, Sep 06 2017 *)

Prog

(PARI) for(n=0, 25, print1(9*binomial(2n, n)^3 - 15*binomial(2n, n)^2 + 9*binomial(2n, n) - 2, ", ")) \\ G. C. Greubel, Sep 06 2017

Crossrefs

Sequence in context: A249348 A366302 A013926 * A007222 A209265 A042515

Adjacent sequences: A110693 A110694 A110695 * A110697 A110698 A110699

Keyword

nonn

Author

Emeric Deutsch, Aug 03 2005

Status

approved