A198590 Odd numbers producing 7 odd numbers in the Collatz iteration.

9, 19, 37, 77, 81, 149, 163, 309, 321, 325, 331, 597, 625, 643, 653, 663, 713, 715, 1237, 1251, 1285, 1301, 1313, 1325, 1339, 1425, 1427, 1431, 1433, 2389, 2501, 2573, 2577, 2613, 2625, 2627, 2653, 2679, 2695, 2851, 2853, 2861, 2865, 2867, 4949, 5005, 5141

Offset

1,1

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..1046

Mathematica

Collatz[n_] := NestWhileList[If[EvenQ[#], #/2, 3 # + 1] &, n, # > 1 &]; t = {}; Do[If[Length[Select[Collatz[n], OddQ]] == 7, AppendTo[t, n]], {n, 1, 10000, 2}]; t
col7Q[n_]:=Length[Select[NestWhileList[If[EvenQ[#], #/2, 3#+1]&, n, #>1&], OddQ]]==7; Select[ Range[1, 5201, 2], col7Q] (* Harvey P. Dale, Sep 25 2023 *)

Crossrefs

Cf. A198584.

Sequence in context: A034056 A195042 A157034 * A297396 A145958 A290245

Adjacent sequences: A198587 A198588 A198589 * A198591 A198592 A198593

Keyword

nonn

Author

T. D. Noe, Oct 31 2011

Status

approved