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A110698 Kekulé numbers for certain benzenoids of trigonal symmetry. 1
9, 104, 3724, 152978, 6772428, 318919354, 15762420826, 808272767014, 42631956711628, 2298618088718378, 126131492134695474, 7020934326396461014, 395480502329858803674, 22501172037539767125398 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

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) = 20*binomial(2n, n)^3 - 18*binomial(2n, n)^2 + 9*binomial(2n, n) - 2.

MAPLE

a:=n->20*binomial(2*n, n)^3-18*binomial(2*n, n)^2+9*binomial(2*n, n)-2; seq(a(n), n=0..16);

MATHEMATICA

Table[20*Binomial[2*n, n]^3 - 18*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(20*binomial(2n, n)^3 - 18*binomial(2n, n)^2 + 9*binomial(2n, n) - 2, ", ")) \\ G. C. Greubel, Sep 06 2017

CROSSREFS

Sequence in context: A083452 A081461 A231646 * A012485 A052503 A261428

Adjacent sequences:  A110695 A110696 A110697 * A110699 A110700 A110701

KEYWORD

nonn

AUTHOR

Emeric Deutsch, Aug 03 2005

STATUS

approved

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Last modified February 26 05:51 EST 2020. Contains 332277 sequences. (Running on oeis4.)