A198587 Odd numbers producing 4 odd numbers in the Collatz iteration.

17, 35, 69, 75, 141, 151, 277, 301, 565, 605, 1109, 1137, 1205, 2261, 2275, 2417, 2421, 4437, 4549, 4821, 4835, 4849, 9045, 9101, 9669, 9685, 9699, 17749, 18197, 19285, 19341, 19397, 19417, 36181, 36405, 38677, 38741, 38797, 38833, 38835, 70997, 72789, 72817

Offset

1,1

Comments

Start with A385110. If k is in sequence then so is 4*k + 1. - Ralf Stephan, Jun 18 2025

Links

Vincenzo Librandi and T. D. Noe, Table of n, a(n) for n = 1..287 (first 134 terms from Vincenzo Librandi)

Mathematica

Collatz[n_] := NestWhileList[If[EvenQ[#], #/2, 3 # + 1] &, n, # > 1 &]; t = {}; Do[If[Length[Select[Collatz[n], OddQ]] == 4, AppendTo[t, n]], {n, 1, 100000, 2}]; t

Crossrefs

Cf. A198584, A385110.

Sequence in context: A239129 A212427 A195047 * A385110 A041570 A041572

Adjacent sequences: A198584 A198585 A198586 * A198588 A198589 A198590

Keyword

nonn

Author

T. D. Noe, Oct 31 2011

Status

approved