Number of 3-multiantichains of an n-set.

Terms

a(0) =1a(1) =2a(2) =6a(3) =28a(4) =190a(5) =1692a(6) =16766a(7) =166028a(8) =1586430a(9) =14580412a(10) =129654526a(11) =1123451628a(12) =9544185470a(13) =79881877532a(14) =661135445886