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A110159 a(n) = (n+1)(n+2)(n+3)(9n^2 + 26n + 20)/120. 0
1, 11, 54, 179, 469, 1050, 2100, 3858, 6633, 10813, 16874, 25389, 37037, 52612, 73032, 99348, 132753, 174591, 226366, 289751, 366597, 458942, 569020, 699270, 852345, 1031121, 1238706, 1478449, 1753949, 2069064, 2427920, 2834920, 3294753 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Kekulé numbers for certain benzenoids.

REFERENCES

S. J. Cyvin and I. Gutman, Kekulé structures in benzenoid hydrocarbons, Lecture Notes in Chemistry, No. 46, Springer, New York, 1988 (pp. 167-170, Table 10.5/II/6).

LINKS

Table of n, a(n) for n=0..32.

FORMULA

G.f.: (1 + 5x + 3x^2)/(1-x)^6.

MAPLE

a:=n->(n+1)*(n+2)*(n+3)*(9*n^2+26*n+20)/120: seq(a(n), n=0..35);

CROSSREFS

Sequence in context: A003867 A059135 A213840 * A061983 A079884 A200172

Adjacent sequences:  A110156 A110157 A110158 * A110160 A110161 A110162

KEYWORD

nonn,easy

AUTHOR

Emeric Deutsch, Nov 18 2005

STATUS

approved

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Last modified August 20 06:04 EDT 2019. Contains 326139 sequences. (Running on oeis4.)