a(0)=1, a(1)=-2; a(n+2) = a(n+1) + a(n) + (period 3: repeat 3, 1, -1).

Terms

a(0) =1a(1) =-2a(2) =2a(3) =1a(4) =2a(5) =6a(6) =9a(7) =14a(8) =26a(9) =41a(10) =66a(11) =110a(12) =177a(13) =286a(14) =466a(15) =753a(16) =1218a(17) =1974a(18) =3193a(19) =5166a(20) =8362a(21) =13529a(22) =21890a(23) =35422a(24) =57313a(25) =92734a(26) =150050a(27) =242785a(28) =392834a(29) =635622