a(n) = a(n-1) + a(n-2) + 1, with a(0) = 1 and a(1) = 9.

Terms

a(0) =1a(1) =9a(2) =11a(3) =21a(4) =33a(5) =55a(6) =89a(7) =145a(8) =235a(9) =381a(10) =617a(11) =999a(12) =1617a(13) =2617a(14) =4235a(15) =6853a(16) =11089a(17) =17943a(18) =29033a(19) =46977a(20) =76011a(21) =122989a(22) =199001a(23) =321991a(24) =520993a(25) =842985a(26) =1363979a(27) =2206965a(28) =3570945a(29) =5777911