Number of proper (n,3)-clusterings.

Terms

a(0) =1a(1) =38a(2) =675a(3) =7840a(4) =74291a(5) =630546a(6) =5014843a(7) =38290580a(8) =284670771a(9) =2078666854a(10) =14991726971a(11) =107192696520a(12) =761785678291