Number of bracelets of length n using exactly three different colored beads.

Terms

a(0) =0a(1) =0a(2) =1a(3) =6a(4) =18a(5) =56a(6) =147a(7) =411a(8) =1084a(9) =2979a(10) =8043a(11) =22244a(12) =61278a(13) =171030a(14) =477929a(15) =1345236a(16) =3795750a(17) =10758902a(18) =30572427a(19) =87149124a(20) =248991822a(21) =713096352a(22) =2046303339a(23) =5883433409a(24) =16944543810a(25) =48879769575