Numbers n in S000942.
3, 7, 9, 27, 703, 937, 1249, 2223, 2463, 2919, 10087, 13449, 35655, 60975, 142587, 381727, 626331, 837799, 1126015, 1394431, 6206655, 6649279
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][[1]]
Cf. S000942.
nonn,more
T. D. Noe, Aug 29 2016