Maximal term in Collatz-iteration started at 3^n-1.

Terms

a(0) =2a(1) =8a(2) =40a(3) =80a(4) =9232a(5) =9232a(6) =3280a(7) =6560a(8) =29524a(9) =59048a(10) =1276936a(11) =1276936a(12) =6810136a(13) =6810136a(14) =21523360a(15) =43046720a(16) =1570824736a(17) =1570824736a(18) =1743392200a(19) =3486784400a(20) =17651846032a(21) =31381059608a(22) =141214768240a(23) =282429536480