|
|
A114241
|
|
a(n) = (n+1)*(n+2)*(n+3)*(11*n^2 + 29*n + 20)/120.
|
|
1
|
|
|
1, 12, 61, 206, 546, 1232, 2478, 4572, 7887, 12892, 20163, 30394, 44408, 63168, 87788, 119544, 159885, 210444, 273049, 349734, 442750, 554576, 687930, 845780, 1031355, 1248156, 1499967, 1790866, 2125236, 2507776, 2943512, 3437808
(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. 168).
|
|
LINKS
|
|
|
FORMULA
|
a(n) = 6*a(n-1) - 15*a(n-2) + 20*a(n-3) - 15*a(n-4) + 6*a(n-5) - a(n-6) for n > 5.
G.f.: (4*x^2 + 6*x + 1)/(x - 1)^6. (End)
E.g.f.: (120 + 1320*x + 2280*x^2 + 1160*x^3 + 205*x^4 + 11*x^5)*exp(x)/5!. - G. C. Greubel, Nov 11 2018
|
|
MAPLE
|
a:=n->(n+1)*(n+2)*(n+3)*(11*n^2+29*n+20)/120: seq(a(n), n=0..38);
|
|
MATHEMATICA
|
Table[Binomial[n+3, 3]*(11*n^2 +29*n +20)/20, {n, 0, 20}] (* G. C. Greubel, Nov 11 2018 *)
|
|
PROG
|
(PARI) vector(35, n, n--; binomial(n+3, 3)*(11*n^2 +29*n +20)/20) \\ G. C. Greubel, Nov 11 2018
(Magma) [Binomial(n+3, 3)*(11*n^2 +29*n +20)/20: n in [0..35]]; // G. C. Greubel, Nov 11 2018
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,easy
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|