Number of 2-Abelian equivalence classes of words of length n over an alphabet of size 3.

Terms

a(0) =1a(1) =3a(2) =9a(3) =27a(4) =75a(5) =186a(6) =414a(7) =840a(8) =1578a(9) =2784a(10) =4662a(11) =7476a(12) =11556a(13) =17313a(14) =25245a(15) =35955a(16) =50157a(17) =68697a(18) =92559a(19) =122889a(20) =161001a(21) =208404a(22) =266808a(23) =338154a(24) =424620a(25) =528654a(26) =652980a(27) =800634a(28) =974970a(29) =1179699