OFFSET
0,3
COMMENTS
A multiset partition is a finite multiset of finite nonempty multisets. It is achiral if it is not changed by any permutation of the vertices.
EXAMPLE
Non-isomorphic representatives of the a(1) = 1 through a(5) = 9 multiset partitions:
{1} {11} {111} {1111} {11111}
{12} {123} {1122} {12345}
{1}{1} {1}{11} {1234} {1}{1111}
{1}{2} {1}{1}{1} {1}{111} {11}{111}
{1}{2}{3} {11}{11} {1}{1}{111}
{11}{22} {1}{11}{11}
{12}{12} {1}{1}{1}{11}
{1}{1}{11} {1}{1}{1}{1}{1}
{1}{2}{12} {1}{2}{3}{4}{5}
{1}{1}{1}{1}
{1}{1}{2}{2}
{1}{2}{3}{4}
Non-isomorphic representatives of the a(6) = 30 multiset partitions:
{111111} {1}{11111} {1}{1}{1111} {1}{1}{1}{111} {1}{1}{1}{1}{11}
{111222} {11}{1111} {1}{11}{111} {1}{1}{11}{11} {1}{1}{2}{2}{12}
{112233} {111}{111} {11}{11}{11} {1}{2}{11}{22}
{123456} {111}{222} {11}{12}{22} {1}{2}{12}{12}
{112}{122} {11}{22}{33} {1}{2}{3}{123} {1}{1}{1}{1}{1}{1}
{12}{1122} {1}{2}{1122} {1}{1}{1}{2}{2}{2}
{123}{123} {12}{12}{12} {1}{1}{2}{2}{3}{3}
{12}{13}{23} {1}{2}{3}{4}{5}{6}
CROSSREFS
Planted achiral trees are A003238.
Achiral set-systems are counted by A083323.
BII-numbers of achiral set-systems are A330217.
Achiral integer partitions are counted by A330224.
Non-isomorphic fully chiral multiset partitions are A330227.
MM-numbers of achiral multisets of multisets are A330232.
Achiral factorizations are A330234.
KEYWORD
nonn,more
AUTHOR
Gus Wiseman, Dec 07 2019
STATUS
approved