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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A059946 Number of 5-block bicoverings of an n-set. 3
0, 0, 0, 25, 472, 6185, 70700, 759045, 7894992, 80736625, 817897300, 8241325565, 82783813112, 830046591465, 8313655213500, 83215436364085, 832626645756832, 8329096006484705, 83307920631515300, 833180902353754605, 8332418928963358152, 83327847634888960345 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

REFERENCES

I. P. Goulden and D. M. Jackson, Combinatorial Enumeration, John Wiley and Sons, N.Y., 1983.

LINKS

Table of n, a(n) for n=1..22.

Index entries for linear recurrences with constant coefficients, signature (26,-255,1210,-2924,3384,-1440).

FORMULA

a(n)=(1/5!)*(10^n-5*6^n-10*4^n+20*3^n+30*2^n-60). 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).

G.f.: x^4*(288*x^2-178*x+25) / ((x-1)*(2*x-1)*(3*x-1)*(4*x-1)*(6*x-1)*(10*x-1)). [Colin Barker, Jan 11 2013]

MATHEMATICA

With[{c=(1/5!)}, Table[c(10^n-5 6^n-10 4^n+20 3^n+30 2^n-60), {n, 20}]]  (* Harvey P. Dale, Apr 21 2011 *)

CROSSREFS

Cf. A002718, A059443, A003462, A059945, A059947-A059951.

Sequence in context: A056069 A089386 A014927 * A118445 A000497 A028341

Adjacent sequences:  A059943 A059944 A059945 * A059947 A059948 A059949

KEYWORD

easy,nonn

AUTHOR

Vladeta Jovovic, Feb 14 2001

EXTENSIONS

More terms from Colin Barker, Jan 11 2013

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 May 25 03:14 EDT 2019. Contains 323539 sequences. (Running on oeis4.)