Number of 2n-bead necklaces labeled with numbers 1..4 not allowing reversal, with neighbors differing by exactly 1.

A208723

Number of 2n-bead necklaces labeled with numbers 1..4 not allowing reversal, with neighbors differing by exactly 1.

Terms

    a(0) =3a(1) =5a(2) =8a(3) =15a(4) =27a(5) =60a(6) =123a(7) =285a(8) =648a(9) =1529a(10) =3603a(11) =8680a(12) =20883a(13) =50825a(14) =124056a(15) =304575a(16) =750123a(17) =1855100a(18) =4600203a(19) =11442087a(20) =28527448a(21) =71292605a(22) =178526883a(23) =447919420a(24) =1125750147a(25) =2833906685a(26) =7144450568a(27) =18036423975a(28) =45591631803a(29) =115381823348

External references