A327436 Number of connected, unlabeled antichains of nonempty subsets of {1..n} covering n vertices with at least one cut-vertex (vertex-connectivity 1).

0, 0, 1, 1, 4, 29

Offset

0,5

Links

Table of n, a(n) for n=0..5.

Formula

a(n > 2) = A261006(n) - A305028(n).

Example

Non-isomorphic representatives of the a(2) = 1 through a(5) = 29 antichains:
  {12}  {12}{13}  {12}{134}         {12}{1345}
                  {12}{13}{14}      {123}{145}
                  {12}{13}{24}      {12}{13}{145}
                  {12}{13}{14}{23}  {12}{13}{245}
                                    {13}{24}{125}
                                    {13}{124}{125}
                                    {14}{123}{235}
                                    {12}{13}{14}{15}
                                    {12}{13}{14}{25}
                                    {12}{13}{24}{35}
                                    {12}{13}{14}{235}
                                    {12}{13}{23}{145}
                                    {12}{13}{45}{234}
                                    {12}{14}{23}{135}
                                    {12}{15}{134}{234}
                                    {15}{23}{124}{134}
                                    {15}{123}{124}{134}
                                    {15}{123}{124}{234}
                                    {12}{13}{14}{15}{23}
                                    {12}{13}{14}{23}{25}
                                    {12}{13}{14}{23}{45}
                                    {12}{13}{15}{24}{34}
                                    {12}{13}{14}{15}{234}
                                    {12}{13}{14}{25}{234}
                                    {12}{13}{14}{15}{23}{24}
                                    {12}{13}{14}{15}{23}{45}
                                    {12}{13}{14}{23}{24}{35}
                                    {15}{123}{124}{134}{234}
                                    {12}{13}{14}{15}{23}{24}{34}

Crossrefs

Column k = 1 of A327359.

The labeled version is A327356.

Cf. A006602, A014466, A048143, A261005, A326704, A326786, A327112, A327114, A327426, A327334, A327336, A327350, A327351, A327358.

Sequence in context: A202713 A129290 A307553 * A339266 A247278 A278823

Adjacent sequences: A327433 A327434 A327435 * A327437 A327438 A327439

Keyword

nonn

Author

Gus Wiseman, Sep 11 2019

Status

approved