login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 56th year, we are closing in on 350,000 sequences, and we’ve crossed 9,700 citations (which often say “discovered thanks to the OEIS”).

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

Andrew Howroyd, Table of n, a(n) for n = 1..200

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 *)

PROG

(PARI) a(n) = {(1/5!)*(10^n - 5*6^n - 10*4^n + 20*3^n + 30*2^n - 60)} \\ Andrew Howroyd, Jan 29 2020

CROSSREFS

Column k=5 of A059443.

Cf. A002718.

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 December 7 19:20 EST 2021. Contains 349585 sequences. (Running on oeis4.)