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

Terms

a(0) =0a(1) =1a(2) =3a(3) =4a(4) =9a(5) =15a(6) =24a(7) =41a(8) =67a(9) =108a(10) =177a(11) =287a(12) =464a(13) =753a(14) =1219a(15) =1972a(16) =3193a(17) =5167a(18) =8360a(19) =13529a(20) =21891a(21) =35420a(22) =57313a(23) =92735a(24) =150048a(25) =242785a(26) =392835a(27) =635620a(28) =1028457a(29) =1664079