The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A006025 Number of labeled mating digraphs with n nodes. (Formerly M3160) 6
 1, 1, 3, 54, 3750, 1009680, 1058347920, 4375678520640, 71934792452208000, 4719774805970453006400, 1237727595442264073683462080, 1298006134163762816201615178698880, 5444432200219729912412940250057668378240 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 REFERENCES N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS Andrew Howroyd, Table of n, a(n) for n = 0..50 R. C. Read, The enumeration of mating-type graphs, Report CORR 89-38, Dept. Combinatorics and Optimization, Univ. Waterloo, 1989. FORMULA a(n) = Sum_{k=0..n} Stirling1(n, k)*2^(k^2-k). - Vladeta Jovovic, Feb 11 2003 E.g.f.: Sum_{n>=0} 2^(n*(n-1))*log(1+x)^n/n!. - Paul D. Hanna, May 20 2009 MATHEMATICA a[0] = 1; a[n_] := Sum[StirlingS1[n , k]*2^(k^2 - k), {k, 0, n}]; Table[a[n], {n, 0, 12}] (* Jean-François Alcover, Aug 16 2019 *) PROG (PARI) a(n)=n!*polcoeff(sum(k=0, n, 2^(k*(k-1))*log(1+x+x*O(x^n))^k/k!), n) \\ Paul D. Hanna, May 20 2009 CROSSREFS Cf. A006024. Sequence in context: A091826 A091796 A171213 * A049414 A003027 A054545 Adjacent sequences: A006022 A006023 A006024 * A006026 A006027 A006028 KEYWORD nonn AUTHOR Simon Plouffe EXTENSIONS More terms from Vladeta Jovovic, Feb 11 2003 a(0)=1 prepended by Andrew Howroyd, Sep 09 2018 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified February 24 13:52 EST 2024. Contains 370303 sequences. (Running on oeis4.)