|
Search: id:A059950
|
|
|
| A059950 |
|
Number of 9-block bicoverings of an n-set. |
|
+0
4
|
|
| 0, 0, 0, 0, 0, 15, 8456, 954213, 66253552, 3622342095, 172672602432, 7557346901841, 312733696544984, 12456923582109435, 483124650731622328, 18383758048494864909, 689931203330381971296, 25630900118611348761735
(list; graph; listen)
|
|
|
OFFSET
|
1,6
|
|
|
REFERENCES
|
I. P. Goulden and D. M. Jackson, Combinatorial Enumeration, John Wiley and Sons, N.Y., 1983.
|
|
FORMULA
|
a(n)=(1/9!)*(36^n-9*28^n-36*22^n+72*21^n+252*16^n-336*15^n+378*12^n-1512*11^n+1260*10^n-1890*8^n+5040*7^n-4536*6^n+7560*5^n-8820*4^n-11256*3^n+28728*2^n-19152). E.g.f. for m-block bicoverings of an n-set is exp(-x-1/2*x^2*(exp(y)-1))*Sum_{i=0..inf} x^i/i!*exp(binomial(i, 2)*y).
|
|
CROSSREFS
|
Cf. A002718, A059443, A003462, A059945-A059949, A059951.
Sequence in context: A066968 A113795 A074488 this_sequence A140285 A112614 A068732
Adjacent sequences: A059947 A059948 A059949 this_sequence A059951 A059952 A059953
|
|
KEYWORD
|
easy,nonn
|
|
AUTHOR
|
Vladeta Jovovic (vladeta(AT)eunet.rs), Feb 14 2001
|
|
|
Search completed in 0.002 seconds
|
