Numbers k in S000942.
5, 12, 13, 102, 131, 133, 134, 141, 159, 165, 170, 171, 222, 254, 273, 282, 310, 342, 364, 380, 406, 492
1
T. D. Noe, Plot of 22 terms
Eric W. Weinstein, MathWorld: Collatz Problem
(Mma) Collatz[n_] := NestWhileList[If[EvenQ[#], #/2, 3 # + 1] &, n, # > 1 &]; t = {}; mx = 0; Do[len = Length[Select[Collatz[n], # > n &]]; If[len > mx, mx = len; AppendTo[t, {n, mx}]];, {n, 100000}]; Transpose[t][[2]]
Cf. S000942.
nonn,more
T. D. Noe, Aug 29 2016