A306417 Number of self-conjugate set partitions of {1, ..., n}.

1, 1, 0, 1, 1, 2, 7, 7, 46, 39, 321

Offset

0,6

Comments

This sequence counts set partitions fixed under Callan's conjugation operation.

Links

Table of n, a(n) for n=0..10.

David Callan, On conjugates for set partitions and integer compositions, arXiv:math/0508052 [math.CO], 2005.

Example

The  a(3) = 1 through a(7) = 7 self-conjugate set partitions:
  {{12}{3}}  {{13}{24}}  {{123}{4}{5}}  {{135}{246}}    {{13}{246}{57}}
                         {{13}{2}{45}}  {{124}{35}{6}}  {{15}{246}{37}}
                                        {{13}{25}{46}}  {{1234}{5}{6}{7}}
                                        {{14}{2}{356}}  {{124}{3}{56}{7}}
                                        {{14}{236}{5}}  {{134}{2}{5}{67}}
                                        {{14}{25}{36}}  {{14}{2}{3}{567}}
                                        {{145}{26}{3}}  {{14}{23}{57}{6}}

Crossrefs

Cf. A000110, A000126, A000296, A001610, A032032, A052841, A080107, A169985, A306416, A324011, A324012.

Sequence in context: A090523 A164314 A156003 * A011416 A086658 A272182

Adjacent sequences: A306414 A306415 A306416 * A306418 A306419 A306420

Keyword

nonn,more

Author

Gus Wiseman, Feb 14 2019

Status

approved