Number of tree-like octagonal systems.

Terms

a(0) =1a(1) =1a(2) =3a(3) =11a(4) =56a(5) =341a(6) =2351a(7) =17329a(8) =133126a(9) =1052813a(10) =8511339a(11) =70050568a(12) =585226579a(13) =4952310082a(14) =42376979857a(15) =366185395267