a(0) = 1, a(1) = 2, a(2) = 5; for n >= 3, a(n) = a(n - 1) - 2*a(n - 2) + a(n - 3).

Terms

a(0) =1a(1) =2a(2) =5a(3) =2a(4) =-6a(5) =-5a(6) =9a(7) =13a(8) =-10a(9) =-27a(10) =6a(11) =50a(12) =11a(13) =-83a(14) =-55a(15) =122a(16) =149a(17) =-150a(18) =-326a(19) =123a(20) =625a(21) =53a(22) =-1074a(23) =-555a(24) =1646a(25) =1682a(26) =-2165a(27) =-3883a(28) =2129a(29) =7730