Number of n-bead necklace structures with beads of exactly four colors and no adjacent beads having the same color.

A328130

Number of n-bead necklace structures with beads of exactly four colors and no adjacent beads having the same color.

Terms

    a(0) =0a(1) =0a(2) =0a(3) =1a(4) =1a(5) =5a(6) =10a(7) =33a(8) =83a(9) =237a(10) =640a(11) =1817a(12) =5005a(13) =14099a(14) =39504a(15) =111585a(16) =315235a(17) =894845a(18) =2544220a(19) =7256607a(20) =20738097a(21) =59405343a(22) =170488450a(23) =490221899a(24) =1411923987a(25) =4073098085a(26) =11767069378a(27) =34041318969a(28) =98603778565a(29) =285954140473

External references