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

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A136723 Number of preferential arrangements (or hierarchical orderings) on the connected graphs on n labeled nodes. 2
1, 1, 3, 52, 2850, 393848, 125054832, 88260845008, 137304025714320, 469859118159233792, 3527181890877230433408, 57833314494643038031674112, 2060645597746315164145860149760, 158727775101107953869596632383822848 (list; graph; refs; listen; history; internal format)
OFFSET

1,3

COMMENTS

Figure n3 demonstrates all 4*13=52 hierarchical orderings on n=3 connected points. In addition, the pink pictures describe the 10 cases where not all or no points are connected.

LINKS

Thomas Wieder, Figure n3

FORMULA

a(n)=A001187(n)*A000670(n);

EXAMPLE

There is A001187(2)=1 connected graph for n=2 labeled elements: The chain 1-2.

The chain gives us 3 hierarchical orderings:

1-2

1

|

2

2

|

1

CROSSREFS

Cf. A001187, A000670, A136722, A034691, A075729.

Sequence in context: A202654 A030180 A005547 * A202649 A143387 A082484

Adjacent sequences:  A136720 A136721 A136722 * A136724 A136725 A136726

KEYWORD

easy,nonn

AUTHOR

Thomas Wieder (thomas.wieder(AT)t-online.de), Jan 19 2008; corrected Jan 19 2008

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Transforms | Puzzles | Hot | Classics
Recent Additions | More pages | Superseeker | Maintained by The OEIS Foundation Inc.

Content is available under The OEIS End-User License Agreement .

Last modified February 15 12:18 EST 2012. Contains 205785 sequences.