A (1,2) Somos-4 sequence.

Terms

a(0) =0a(1) =1a(2) =1a(3) =-2a(4) =1a(5) =9a(6) =-16a(7) =-73a(8) =-145a(9) =1442a(10) =3951a(11) =-49121a(12) =273184a(13) =4095073a(14) =-13134671a(15) =-609740514a(16) =-7877081935a(17) =206841213449a(18) =153991537616