x->x/2 if x even, x->3x-1 if x odd.

Terms

a(0) =89a(1) =266a(2) =133a(3) =398a(4) =199a(5) =596a(6) =298a(7) =149a(8) =446a(9) =223a(10) =668a(11) =334a(12) =167a(13) =500a(14) =250a(15) =125a(16) =374a(17) =187a(18) =560a(19) =280a(20) =140a(21) =70a(22) =35a(23) =104a(24) =52a(25) =26a(26) =13a(27) =38a(28) =19a(29) =56