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A199818 Odd numbers producing 20 even numbers in the Collatz iteration. 2
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 (list; graph; refs; listen; history; text; internal format)
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

Sequence in context: A124826 A136069 A140028 * A248401 A136074 A142311

Adjacent sequences:  A199815 A199816 A199817 * A199819 A199820 A199821

KEYWORD

nonn

AUTHOR

Vincenzo Librandi, Nov 12 2011

STATUS

approved

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Last modified November 19 02:01 EST 2018. Contains 317332 sequences. (Running on oeis4.)