Number of pairs of orientable necklaces with n beads and up to 3 colors; i.e., turning the necklace over does not leave it unchanged. The turned-over necklace is not included in the count.
A278639
Number of pairs of orientable necklaces with n beads and up to 3 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) =1a(4) =3a(5) =12a(6) =38a(7) =117a(8) =336a(9) =976a(10) =2724a(11) =7689a(12) =21455a(13) =60228a(14) =168714a(15) =475037a(16) =1338861a(17) =3788400a(18) =10742588a(19) =30556305a(20) =87112059a(21) =248967564a(22) =713032782a(23) =2046325125a(24) =5883428618a(25) =16944975048a(26) =48880471500a(27) =141212377489a(28) =408509453511
External references
- oeis: A278639