a(n) is the number of all two colored bracelets (necklaces with turning over allowed) with n beads with the two colors from a repertoire of n distinct colors, for n>=2.
A214308
a(n) is the number of all two colored bracelets (necklaces with turning over allowed) with n beads with the two colors from a repertoire of n distinct colors, for n>=2.
Terms
- a(0) =1a(1) =6a(2) =24a(3) =60a(4) =165a(5) =336a(6) =784a(7) =1584a(8) =3420a(9) =6820a(10) =14652a(11) =29484a(12) =62335a(13) =128310a(14) =269760a(15) =558960a(16) =1175499a(17) =2446668a(18) =5131900a(19) =10702020a(20) =22385517a(21) =46655224a(22) =97344096a(23) =202555800a(24) =421478200a(25) =875297124a(26) =1816696728a(27) =3764747868a(28) =7795573230a(29) =16121364000
External references
- oeis: A214308