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

Terms

a(0) =0a(1) =1a(2) =1a(3) =1a(4) =3a(5) =6a(6) =11a(7) =21a(8) =41a(9) =79a(10) =152a(11) =293a(12) =565a(13) =1089a(14) =2099a(15) =4046a(16) =7799a(17) =15033a(18) =28977a(19) =55855a(20) =107664a(21) =207529a(22) =400025a(23) =771073a(24) =1486291a(25) =2864918a(26) =5522307a(27) =10644589a(28) =20518105a(29) =39549919