A330124 Number of unlabeled set-systems with n vertices and no endpoints.
1, 1, 2, 22, 1776
Offset: 0
Examples
Non-isomorphic representatives of the a(3) = 22 set-systems:
0
{1}{2}{12}
{12}{13}{23}
{1}{23}{123}
{12}{13}{123}
{1}{2}{13}{23}
{1}{2}{3}{123}
{1}{12}{13}{23}
{1}{2}{13}{123}
{1}{12}{13}{123}
{1}{12}{23}{123}
{12}{13}{23}{123}
{1}{2}{3}{12}{13}
{1}{2}{12}{13}{23}
{1}{2}{3}{12}{123}
{1}{2}{12}{13}{123}
{1}{2}{13}{23}{123}
{1}{12}{13}{23}{123}
{1}{2}{3}{12}{13}{23}
{1}{2}{3}{12}{13}{123}
{1}{2}{12}{13}{23}{123}
{1}{2}{3}{12}{13}{23}{123}
Crossrefs
Partial sums of the covering case A330196.
The labeled version is A330059.
The "multi" version is A302545.
Unlabeled set-systems with no endpoints counted by weight are A330054.
Unlabeled set-systems with no singletons are A317794.
Unlabeled set-systems counted by vertices are A000612.
Unlabeled set-systems counted by weight are A283877.
The case with no singletons is A320665.
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