Number of 7-bead necklaces of n colors not allowing reversal, with no adjacent beads having the same color.

A208537

Number of 7-bead necklaces of n colors not allowing reversal, with no adjacent beads having the same color.

Terms

    a(0) =0a(1) =0a(2) =18a(3) =312a(4) =2340a(5) =11160a(6) =39990a(7) =117648a(8) =299592a(9) =683280a(10) =1428570a(11) =2783880a(12) =5118828a(13) =8964072a(14) =15059070a(15) =24408480a(16) =38347920a(17) =58619808a(18) =87460002a(19) =127695960a(20) =182857140a(21) =257298360a(22) =356336838a(23) =486403632a(24) =655210200a(25) =871930800a(26) =1147401450

External references