a(n) = a(n-1) + a(n-2) + 1 for n>1, a(0)=0, a(1)=5.

Terms

a(0) =0a(1) =5a(2) =6a(3) =12a(4) =19a(5) =32a(6) =52a(7) =85a(8) =138a(9) =224a(10) =363a(11) =588a(12) =952a(13) =1541a(14) =2494a(15) =4036a(16) =6531a(17) =10568a(18) =17100a(19) =27669a(20) =44770a(21) =72440a(22) =117211a(23) =189652a(24) =306864a(25) =496517a(26) =803382a(27) =1299900a(28) =2103283a(29) =3403184