A326898 Number of unlabeled topologies with up to n points.

1, 2, 5, 14, 47, 186, 904, 5439, 41418, 404501, 5122188, 84623842, 1828876351, 51701216248, 1908493827243, 91755916071736, 5729050033597431

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