Number of 2n-bead necklaces labeled with numbers 1..7 allowing reversal, with neighbors differing by exactly 1.

A208670

Number of 2n-bead necklaces labeled with numbers 1..7 allowing reversal, with neighbors differing by exactly 1.

Terms

    a(0) =6a(1) =11a(2) =20a(3) =41a(4) =86a(5) =208a(6) =514a(7) =1398a(8) =3934a(9) =11576a(10) =34850a(11) =107303a(12) =334396a(13) =1053851a(14) =3345320a(15) =10685570a(16) =34292064a(17) =110498897a(18) =357256018a(19) =1158492478a(20) =3766458404a(21) =12274037845a(22) =40082339406a(23) =131144365904a(24) =429838330172

External references