OFFSET
1,1
COMMENTS
MATHEMATICA
Collatz[n_] := NestWhileList[If[EvenQ[#], #/2, 3 # + 1] &, n, # > 1 &]; t = {}; Do[If[Length[Select[Collatz[n], EvenQ]] == 20, AppendTo[t, n]], {n, 1, 100000, 2}]; t
CROSSREFS
KEYWORD
nonn
AUTHOR
Vincenzo Librandi, Nov 12 2011
STATUS
approved