A238193 Position of first occurrence of (4^n - 1)/3 in A238192.

3, 21, 75, 151, 1365, 5461, 14563, 87381, 184111, 932067

Offset: 2

Author

T. D. Noe, Feb 21 2014

Keywords

• nonn
• more

Comments

Another version of A237661.

Is this (apart from the missing 1) the same as A054646? - R. J. Mathar, Mar 30 2014

Crossrefs

Cf. A002450 ((4^n-1)/3), A070165 (Collatz trajectories), A238192.

Programs

Mathematica

Collatz[n_] := NestWhileList[If[EvenQ[#], #/2, 3 # + 1] &, n, # > 1 &]; t = Table[c = Collatz[n]; co = Select[c, OddQ]; If[Length[co] == 1, 0, co[[-2]]], {n, 10000}]; Flatten[Table[Position[t, (4^n - 1)/3, 1, 1], {n, 2, 7}]]