a(1)=2, a(2)=3, then a(n)=a(n-1)+a(n-2) if n odd, a(n)=a(n-1)-a(n-2) if n even.

Terms

a(0) =2a(1) =3a(2) =5a(3) =2a(4) =7a(5) =5a(6) =12a(7) =7a(8) =19a(9) =12a(10) =31a(11) =19a(12) =50a(13) =31a(14) =81a(15) =50a(16) =131a(17) =81a(18) =212a(19) =131a(20) =343a(21) =212a(22) =555a(23) =343a(24) =898a(25) =555a(26) =1453a(27) =898a(28) =2351a(29) =1453