OFFSET
0,3
COMMENTS
A multiset antichain is a finite set of finite nonempty multisets, none of which is a submultiset of any other. The weight of an antichain is the sum of cardinalities (counting multiplicity) of its elements.
FORMULA
Euler transform of A293994.
EXAMPLE
Non-isomorphic representatives of the a(4) = 16 antichains are:
((1111)), ((1112)), ((1122)), ((1123)), ((1234)),
((1)(234)), ((2)(111)), ((2)(113)), ((11)(12)), ((11)(22)), ((11)(23)), ((12)(13)), ((12)(34)),
((1)(2)(34)),((2)(3)(11)),
((1)(2)(3)(4)).
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Gus Wiseman, Oct 21 2017
STATUS
approved