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

Terms

a(0) =1a(1) =1a(2) =0a(3) =0a(4) =2a(5) =3a(6) =5a(7) =10a(8) =20a(9) =38a(10) =73a(11) =141a(12) =272a(13) =524a(14) =1010a(15) =1947a(16) =3753a(17) =7234a(18) =13944a(19) =26878a(20) =51809a(21) =99865a(22) =192496a(23) =371048a(24) =715218a(25) =1378627a(26) =2657389a(27) =5122282a(28) =9873516a(29) =19031814