Number of 2n-bead necklaces labeled with numbers 1..4 allowing reversal, with neighbors differing by exactly 1.

A208667

Number of 2n-bead necklaces labeled with numbers 1..4 allowing reversal, with neighbors differing by exactly 1.

Terms

    a(0) =3a(1) =5a(2) =8a(3) =14a(4) =24a(5) =47a(6) =89a(7) =187a(8) =396a(9) =881a(10) =1990a(11) =4645a(12) =10935a(13) =26211a(14) =63320a(15) =154378a(16) =378444a(17) =933023a(18) =2308957a(19) =5735372a(20) =14286908a(21) =35683815a(22) =89324138a(23) =224057919a(24) =563033979a(25) =1417210457a(26) =3572641304a(27) =9018885122a(28) =22796905056a(29) =57692673963

External references