Least inverse of A115247, or -1 if no inverse exists.

Terms

a(0) =0a(1) =2a(2) =4a(3) =37a(4) =8a(5) =138a(6) =13a(7) =41a(8) =27a(9) =167a(10) =335a(11) =111a(12) =746a(13) =492a(14) =8366a(15) =3032a(16) =7223