OFFSET
2,1
COMMENTS
Another version of A237661.
Is this (apart from the missing 1) the same as A054646? - R. J. Mathar, Mar 30 2014
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}]]
CROSSREFS
KEYWORD
nonn,more
AUTHOR
T. D. Noe, Feb 21 2014
STATUS
approved