Number of pairs of orientable necklaces with n beads and up to 4 colors; i.e., turning the necklace over does not leave it unchanged. The turned-over necklace is not included in the count.
A278640
Number of pairs of orientable necklaces with n beads and up to 4 colors; i.e., turning the necklace over does not leave it unchanged. The turned-over necklace is not included in the count.
Terms
- a(0) =0a(1) =0a(2) =0a(3) =4a(4) =15a(5) =72a(6) =270a(7) =1044a(8) =3795a(9) =14060a(10) =51204a(11) =188604a(12) =694130a(13) =2572920a(14) =9567090a(15) =35758704a(16) =134137875a(17) =505159200a(18) =1908554190a(19) =7233104844a(20) =27486506268a(21) =104713296760a(22) =399817262550
External references
- oeis: A278640