a(n) = a(n-1) + a(n-2) + 1 if n is a multiple of 6, otherwise a(n) = a(n-1) + a(n-2).

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =5a(5) =8a(6) =14a(7) =22a(8) =36a(9) =58a(10) =94a(11) =152a(12) =247a(13) =399a(14) =646a(15) =1045a(16) =1691a(17) =2736a(18) =4428a(19) =7164a(20) =11592a(21) =18756a(22) =30348a(23) =49104a(24) =79453a(25) =128557a(26) =208010a(27) =336567a(28) =544577a(29) =881144