A198592 Odd numbers producing 9 odd numbers in the Collatz iteration.

33, 65, 67, 131, 133, 261, 269, 273, 289, 525, 529, 533, 547, 555, 571, 577, 579, 583, 633, 635, 1045, 1059, 1077, 1093, 1099, 1111, 1143, 1155, 1157, 1167, 1177, 1267, 1271, 1273, 2101, 2117, 2123, 2133, 2161, 2189, 2199, 2221, 2285, 2309, 2317, 2321, 2333

Offset: 1

Author

T. D. Noe, Oct 31 2011

Keywords

• nonn

Links

• T. D. Noe, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A198584.

Programs

Mathematica

Collatz[n_] := NestWhileList[If[EvenQ[#], #/2, 3 # + 1] &, n, # > 1 &]; t = {}; Do[If[Length[Select[Collatz[n], OddQ]] == 9, AppendTo[t, n]], {n, 1, 10000, 2}]; t
col9Q[n_]:=Count[NestWhileList[If[EvenQ[#],#/2,3#+1]&,n,#!=1&],?(OddQ[#]&)]==9; Select[ Range[1,2501,2],col9Q] (* _Harvey P. Dale, Dec 10 2023 *)