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

 

Logo


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 A188358 A228218

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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified June 27 15:02 EDT 2017. Contains 288790 sequences.