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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A075756 Number of hierarchies of hierarchies of hierarchies on n points. 1
1, 1, 6, 52, 588, 8174, 134537, 2554647, 54909468, 1316675221, 34820961457, 1006230148609, 31529224324159, 1064355502971193, 38497326001639439, 1484865225798412485, 60822449267067095601, 2636248249383130776940, 120520100503562054999860, 5794815395039941996204424 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..19.

N. J. A. Sloane and Thomas Wieder, The Number of Hierarchical Orderings, arXiv:math/0307064 [math.CO], 2003; Order 21 (2004), 83-89.

FORMULA

E.g.f.: exp(f(x)-1) where f(x) = e.g.f. for A075744.

MATHEMATICA

m = 20;

f[x_] = E^(-1 + E^(-1 + 1/(2 - E^x)));

CoefficientList[Exp[f[x] - 1] + O[x]^m, x]*Range[0, m - 1]! (* Jean-Fran├žois Alcover, Feb 24 2019 *)

CROSSREFS

Cf. A075729, A075744.

Sequence in context: A232821 A127133 A243249 * A217486 A144345 A294158

Adjacent sequences:  A075753 A075754 A075755 * A075757 A075758 A075759

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Oct 15 2002

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 September 18 14:45 EDT 2020. Contains 337169 sequences. (Running on oeis4.)