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

A056332

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

Terms

    a(0) =1a(1) =1a(2) =3a(3) =8a(4) =24a(5) =65a(6) =195a(7) =564a(8) =1677a(9) =4976a(10) =14883a(11) =44452a(12) =133224a(13) =399113a(14) =1196808a(15) =3588840a(16) =10764960a(17) =32289855a(18) =96864963a(19) =290580040a(20) =871725426a(21) =2615132465a(22) =7845353475a(23) =23535926760a(24) =70607649816a(25) =211822550576

External references