4-step Fibonacci sequence starting with 1, 1, 1, 0.

Terms

a(0) =1a(1) =1a(2) =1a(3) =0a(4) =3a(5) =5a(6) =9a(7) =17a(8) =34a(9) =65a(10) =125a(11) =241a(12) =465a(13) =896a(14) =1727a(15) =3329a(16) =6417a(17) =12369a(18) =23842a(19) =45957a(20) =88585a(21) =170753a(22) =329137a(23) =634432a(24) =1222907a(25) =2357229a(26) =4543705a(27) =8758273a(28) =16882114a(29) =32541321