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

Terms

a(0) =0a(1) =4a(2) =3a(3) =6a(4) =8a(5) =13a(6) =20a(7) =32a(8) =51a(9) =82a(10) =132a(11) =213a(12) =344a(13) =556a(14) =899a(15) =1454a(16) =2352a(17) =3805a(18) =6156a(19) =9960a(20) =16115a(21) =26074a(22) =42188a(23) =68261a(24) =110448a(25) =178708a(26) =289155a(27) =467862a(28) =757016a(29) =1224877