a(n) = a(n-1) - (-1)^n*a(n-2), a(0)=0, a(1)=1.

Terms

a(0) =0a(1) =1a(2) =1a(3) =2a(4) =1a(5) =3a(6) =2a(7) =5a(8) =3a(9) =8a(10) =5a(11) =13a(12) =8a(13) =21a(14) =13a(15) =34a(16) =21a(17) =55a(18) =34a(19) =89a(20) =55a(21) =144a(22) =89a(23) =233a(24) =144a(25) =377a(26) =233a(27) =610a(28) =377a(29) =987