|
Search: id:A107979
|
|
|
| A107979 |
|
a(n)=4a(n-1)+2a(n-2), a(0)=2, a(1)=9. |
|
+0
1
|
|
| 2, 9, 40, 178, 792, 3524, 15680, 69768, 310432, 1381264, 6145920, 27346208, 121676672, 541399104, 2408949760, 10718597248, 47692288512, 212206348544, 944209971200, 4201252581888, 18693430269952, 83176226243584
(list; graph; listen)
|
|
|
OFFSET
|
0,1
|
|
|
COMMENT
|
Kekule numbers for certain benzenoids.
|
|
REFERENCES
|
S. J. Cyvin and I. Gutman, Kekule structures in benzenoid hydrocarbons, Lecture Notes in Chemistry, No. 46, Springer, New York, 1988 (p. 78).
|
|
FORMULA
|
O.g.f.: (2+x)/(1-4x-2x^2). a(n)=2*A090017(n)+A090017(n-1). [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Aug 24 2008]
|
|
MAPLE
|
a[0]:=2: a[1]:=9: for n from 2 to 26 do a[n]:=4*a[n-1]+2*a[n-2] od: seq(a[n], n=0..26);
|
|
CROSSREFS
|
Cf. A021001. [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Aug 24 2008]
Sequence in context: A097070 A164033 A020728 this_sequence A021001 A038112 A052512
Adjacent sequences: A107976 A107977 A107978 this_sequence A107980 A107981 A107982
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Emeric Deutsch (deutsch(AT)duke.poly.edu), Jun 12 2005
|
|
|
Search completed in 0.002 seconds
|
