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

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!)
 A059949 Number of 8-block bicoverings of an n-set. 2

%I

%S 0,0,0,0,0,535,51640,2771685,114713760,4127125695,136631722920,

%T 4292250804985,130278290187760,3863262740532195,112733098867629240,

%U 3252644718804860925,93093809127731630400,2649006256251644780935

%N Number of 8-block bicoverings of an n-set.

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

%H Vincenzo Librandi, <a href="/A059949/b059949.txt">Table of n, a(n) for n = 1..100</a>

%F a(n) = (1/8!)*(28^n - 8*21^n - 28*16^n + 56*15^n + 168*11^n - 224*10^n + 210*8^n - 840*7^n + 700*6^n - 840*5^n + 1925*4^n + 1064*3^n - 5460*2^n + 4368).

%F 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).

%F G.f.: -5*x^6*(3390266880*x^8 -3368778336*x^7 +1334596314*x^6 -268312855*x^5 +27919999*x^4 -1171492*x^3 -29534*x^2 +4331*x -107) / ((x -1)*(2*x -1)*(3*x- 1)*(4*x -1)*(5*x -1)*(6*x -1)*(7*x -1)*(8*x -1)*(10*x -1)*(11*x -1)*(15*x -1)*(16*x -1)*(21*x -1)*(28*x -1)). - _Colin Barker_, Jul 08 2013

%Y Column k=8 of A059443.

%Y Cf. A002718.

%K easy,nonn

%O 1,6

%A _Vladeta Jovovic_, Feb 14 2001

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.

Last modified December 8 17:01 EST 2021. Contains 349596 sequences. (Running on oeis4.)