A199818 Odd numbers producing 20 even numbers in the Collatz iteration.

43, 131, 133, 397, 405, 433, 435, 441, 475, 1237, 1251, 1285, 1301, 1313, 1325, 1339, 1425, 1427, 1431, 1433, 3861, 3925, 3939, 3941, 3981, 4017, 4019, 4043, 4277, 4293, 4297, 4301, 11605, 11829, 12053, 12131, 12133, 12853, 12885, 12893, 12913, 12931, 36181

Offset

1,1

Comments

For n <10000000, more terms: 36405, 38677, 38741, 38797, 38833, 38835, 116053, 116501, 349525.

See row 20 of A199636. There are A131450(20) = 52 terms. - T. D. Noe, Nov 18 2011

Links

Table of n, a(n) for n=1..43.

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

Cf. A199636.

Sequence in context: A124826 A136069 A140028 * A248401 A136074 A356727

Adjacent sequences: A199815 A199816 A199817 * A199819 A199820 A199821

Keyword

nonn

Author

Vincenzo Librandi, Nov 12 2011

Status

approved