Number of n-bead necklaces with 4 colors.

Terms

a(0) =1a(1) =4a(2) =10a(3) =24a(4) =70a(5) =208a(6) =700a(7) =2344a(8) =8230a(9) =29144a(10) =104968a(11) =381304a(12) =1398500a(13) =5162224a(14) =19175140a(15) =71582944a(16) =268439590a(17) =1010580544a(18) =3817763740a(19) =14467258264a(20) =54975633976a(21) =209430787824a(22) =799645010860