OFFSET
0,6
COMMENTS
This sequence counts set partitions fixed under Callan's conjugation operation.
LINKS
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
KEYWORD
nonn,more
AUTHOR
Gus Wiseman, Feb 14 2019
STATUS
approved