Trajectory of 3 under map n->7n+1 if n odd, n->n/2 if n even.

Terms

a(0) =3a(1) =22a(2) =11a(3) =78a(4) =39a(5) =274a(6) =137a(7) =960a(8) =480a(9) =240a(10) =120a(11) =60a(12) =30a(13) =15a(14) =106a(15) =53a(16) =372a(17) =186a(18) =93a(19) =652a(20) =326a(21) =163a(22) =1142a(23) =571a(24) =3998a(25) =1999a(26) =13994a(27) =6997a(28) =48980a(29) =24490