a(n) = a(n-1) + a(n-2) + 1 for n>1, a(0)=0, a(1)=4.

Terms

a(0) =0a(1) =4a(2) =5a(3) =10a(4) =16a(5) =27a(6) =44a(7) =72a(8) =117a(9) =190a(10) =308a(11) =499a(12) =808a(13) =1308a(14) =2117a(15) =3426a(16) =5544a(17) =8971a(18) =14516a(19) =23488a(20) =38005a(21) =61494a(22) =99500a(23) =160995a(24) =260496a(25) =421492a(26) =681989a(27) =1103482a(28) =1785472a(29) =2888955