Logo

Greetings from The On-Line Encyclopedia of Integer Sequences!

Hints

Search: id:A001928
Displaying 1-1 of 1 results found. page 1
     Format: long | short | internal | text      Sort: relevance | references | number      Highlight: on | off
A001928 Number of connected topologies with n unlabeled nodes.
(Formerly M1655 N0648)
+0
4
1, 1, 2, 6, 21, 94, 512, 3485, 29515, 314474, 4255727, 73831813, 1653083021, 47941962135, 1803010446411, 87882300251730, 5543501326580737 (list; graph; listen)
OFFSET

0,3

REFERENCES

K. K.-H. Butler and G. Markowsky, Enumeration of finite topologies, Proc. 4th S-E Conf. Combin., Graph Theory, Computing, Congress. Numer. 8 (1973), 169-184.

J. A. Wright, There are 718 6-point topologies, quasi-orderings, and transgraphs, Notices Amer. Math. Soc., 17 (1970), p. 646, Abstract #70T-A106.

J. A. Wright, personal communication.

LINKS

P. J. Cameron, Sequences realized by oligomorphic permutation groups, J. Integ. Seqs. Vol. 3 (2000), #00.1.5.

FORMULA

Inverse Euler transform of A001930. - Vladeta Jovovic (vladeta(AT)Eunet.yu), Jan 06 2006

CROSSREFS

Cf. A001929, A001930.

Sequence in context: A090805 A033540 A115089 this_sequence A005638 A008988 A061232

Adjacent sequences: A001925 A001926 A001927 this_sequence A001929 A001930 A001931

KEYWORD

nonn

AUTHOR

njas

EXTENSIONS

More terms from Vladeta Jovovic (vladeta(AT)Eunet.yu), Jan 06 2006

page 1

Search completed in 0.002 seconds

Lookup | Welcome | Find friends | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Transforms | Puzzles | Hot | Classics
More pages | Superseeker | Maintained by N. J. A. Sloane (njas@research.att.com)

Last modified September 6 16:04 EDT 2008. Contains 143483 sequences.


AT&T Labs Research