Number of 7-bead necklaces of n colors allowing reversal, with no adjacent beads having the same color.

A208545

Number of 7-bead necklaces of n colors allowing reversal, with no adjacent beads having the same color.

Terms

    a(0) =0a(1) =0a(2) =9a(3) =156a(4) =1170a(5) =5580a(6) =19995a(7) =58824a(8) =149796a(9) =341640a(10) =714285a(11) =1391940a(12) =2559414a(13) =4482036a(14) =7529535a(15) =12204240a(16) =19173960a(17) =29309904a(18) =43730001a(19) =63847980a(20) =91428570a(21) =128649180a(22) =178168419a(23) =243201816a(24) =327605100a(25) =435965400a(26) =573700725a(27) =747168084

External references