Number of n-bead necklaces of 4 colors allowing reversal, with no adjacent beads having the same color.

A208540

Number of n-bead necklaces of 4 colors allowing reversal, with no adjacent beads having the same color.

Terms

    a(0) =4a(1) =6a(2) =4a(3) =21a(4) =24a(5) =92a(6) =156a(7) =498a(8) =1096a(9) =3210a(10) =8052a(11) =22913a(12) =61320a(13) =173088a(14) =478316a(15) =1351983a(16) =3798240a(17) =10781954a(18) =30585828a(19) =87230157a(20) =249056136a(21) =713387076a(22) =2046590844a(23) =5884491500a(24) =16945772208a(25) =48883660146a(26) =141214768972

External references