Number of primitive (aperiodic) reversible string structures with n beads using exactly three different colors.

A056337

Number of primitive (aperiodic) reversible string structures with n beads using exactly three different colors.

Terms

    a(0) =0a(1) =0a(2) =1a(3) =4a(4) =15a(5) =49a(6) =160a(7) =498a(8) =1544a(9) =4715a(10) =14356a(11) =43420a(12) =131145a(13) =394990a(14) =1188564a(15) =3572400a(16) =10732065a(17) =32224216a(18) =96733636a(19) =290317660a(20) =871200664a(21) =2614083394a(22) =7843255300a(23) =23531731530a(24) =70599259170a(25) =211805771345

External references