A198587 - OEIS

%I #14 Apr 11 2021 08:10:37

%S 17,35,69,75,141,151,277,301,565,605,1109,1137,1205,2261,2275,2417,

%T 2421,4437,4549,4821,4835,4849,9045,9101,9669,9685,9699,17749,18197,

%U 19285,19341,19397,19417,36181,36405,38677,38741,38797,38833,38835,70997,72789,72817

%N Odd numbers producing 4 odd numbers in the Collatz iteration.

%H Vincenzo Librandi and T. D. Noe, <a href="/A198587/b198587.txt">Table of n, a(n) for n = 1..287</a> (first 134 terms from Vincenzo Librandi)

%t 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

%Y Cf. A198584.

%K nonn

%O 1,1

%A _T. D. Noe_, Oct 31 2011