Number of primitive (period n) bracelets using exactly three different colored beads.

Terms

a(0) =0a(1) =0a(2) =1a(3) =6a(4) =18a(5) =55a(6) =147a(7) =405a(8) =1083a(9) =2961a(10) =8043a(11) =22182a(12) =61278a(13) =170883a(14) =477910a(15) =1344825a(16) =3795750a(17) =10757763a(18) =30572427a(19) =87146139a(20) =248991674a(21) =713088309a(22) =2046303339a(23) =5883410760a(24) =16944543792a(25) =48879708297