login
This site is supported by donations to The OEIS Foundation.

 

Logo

Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing.
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A108683 a(n) = (n+1)*(n+2)*(n+3)*(n+4)*(7*n^2 + 20*n + 15)/360. 0
1, 14, 83, 322, 966, 2436, 5418, 10956, 20559, 36322, 61061, 98462, 153244, 231336, 340068, 488376, 687021, 948822, 1288903, 1724954, 2277506, 2970220, 3830190, 4888260, 6179355, 7742826, 9622809, 11868598, 14535032, 17682896, 21379336 (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 (p. 233, # 8).

LINKS

Table of n, a(n) for n=0..30.

FORMULA

G.f.: (1+x)*(1+6*x)/(1-x)^7.

MAPLE

G:=factor(sum(a(n)*z^n, n=0..infinity)); series(G, z=0, 37);

CROSSREFS

Sequence in context: A176010 A250562 A166819 * A323415 A166389 A085036

Adjacent sequences:  A108680 A108681 A108682 * A108684 A108685 A108686

KEYWORD

nonn,easy

AUTHOR

Emeric Deutsch, Jun 18 2005

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 14 12:04 EST 2019. Contains 329979 sequences. (Running on oeis4.)