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

 

Logo

Thanks to everyone who made a donation during our annual appeal!
To see the list of donors, or make a donation, see the OEIS Foundation home page.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A326898 Number of unlabeled topologies with up to n points. 5
1, 2, 5, 14, 47, 186, 904, 5439, 41418, 404501, 5122188, 84623842, 1828876351, 51701216248, 1908493827243, 91755916071736, 5729050033597431 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..16.

EXAMPLE

Non-isomorphic representatives of the a(0) = 1 through a(3) = 14 topologies:

  {}  {}     {}            {}

      {}{1}  {}{1}         {}{1}

             {}{12}        {}{12}

             {}{2}{12}     {}{123}

             {}{1}{2}{12}  {}{2}{12}

                           {}{3}{123}

                           {}{23}{123}

                           {}{1}{2}{12}

                           {}{1}{23}{123}

                           {}{3}{23}{123}

                           {}{2}{3}{23}{123}

                           {}{3}{13}{23}{123}

                           {}{2}{3}{13}{23}{123}

                           {}{1}{2}{3}{12}{13}{23}{123}

CROSSREFS

Partial sums of A001930.

The labeled version is A326878.

Cf. A000612, A000798, A003180, A108800, A193675, A306445, A326867, A326882.

Sequence in context: A317784 A096402 A007268 * A109156 A143918 A129867

Adjacent sequences:  A326895 A326896 A326897 * A326899 A326900 A326901

KEYWORD

nonn

AUTHOR

Gus Wiseman, Aug 02 2019

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 January 19 03:54 EST 2020. Contains 331031 sequences. (Running on oeis4.)