A (1,1) Somos-4 sequence.

Terms

a(0) =1a(1) =2a(2) =-3a(3) =1a(4) =11a(5) =-16a(6) =-35a(7) =-129a(8) =299a(9) =-386a(10) =-3977a(11) =8063a(12) =42489a(13) =269344a(14) =-1000009a(15) =3727745a(16) =47166649a(17) =-123526014a(18) =-1764203419a(19) =-18228952703a(20) =113727892147