login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo

Please make a donation to keep the OEIS running. We are now in our 56th year. In the past year we added 10000 new sequences and reached almost 9000 citations (which often say "discovered thanks to the OEIS").
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A107980 Triangle read by rows: T(n,k)=(n+2)(k+1)(k+2)(k-2n-2)(k-2n-3)/24 for 0<=k<=n. 0
1, 5, 9, 14, 30, 40, 30, 70, 105, 125, 55, 135, 216, 280, 315, 91, 231, 385, 525, 630, 686, 140, 364, 624, 880, 1100, 1260, 1344, 204, 540, 945, 1365, 1755, 2079, 2310, 2430, 285, 765, 1360, 2000, 2625, 3185, 3640, 3960, 4125, 385, 1045, 1881, 2805, 3740 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Kekulé numbers for certain benzenoids. Column 0 yields A000330. Main diagonal yields A006414. Row sums yield A006858.

REFERENCES

S. J. Cyvin and I. Gutman, Kekulé structures in benzenoid hydrocarbons, Lecture Notes in Chemistry, No. 46, Springer, New York, 1988 (p. 237, K{B(n,3,l)}).

LINKS

Table of n, a(n) for n=0..49.

EXAMPLE

Triangle begins:

1;

5,9;

14,30,40;

30,70,105,125;

MAPLE

T:=proc(n, k) if k<=n then 1/24*(n+2)*(k+1)*(k+2)*(k-2*n-2)*(k-2*n-3) else 0 fi end: for n from 0 to 9 do seq(T(n, k), k=0..n) od; # yields sequence in triangular form

CROSSREFS

Cf. A000330, A006414, A006858.

Sequence in context: A109329 A169872 A115380 * A163161 A331556 A188358

Adjacent sequences:  A107977 A107978 A107979 * A107981 A107982 A107983

KEYWORD

nonn,tabl

AUTHOR

Emeric Deutsch, Jun 12 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 1 21:02 EST 2020. Contains 338858 sequences. (Running on oeis4.)