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Numbers k whose Collatz (3x+1) trajectory includes at least one term that is greater than k.
4

%I #26 May 15 2024 09:07:42

%S 3,5,6,7,9,10,11,12,13,14,15,17,18,19,21,22,23,25,26,27,28,29,30,31,

%T 33,34,35,36,37,38,39,41,42,43,44,45,46,47,49,50,51,53,54,55,57,58,59,

%U 60,61,62,63,65,66,67,69,70,71,73,74,75,76,77,78,79,81,82,83

%N Numbers k whose Collatz (3x+1) trajectory includes at least one term that is greater than k.

%H T. D. Noe, <a href="/A213199/b213199.txt">Table of n, a(n) for n = 1..1000</a>

%e a(1) = 3 because 3 is the first number k whose trajectory goes above k.

%t Collatz[n_] := NestWhileList[If[EvenQ[#], #/2, 3 # + 1] &, n, # > 1 &]; Select[Range[100], Max[Collatz[#]] > # &] (* _T. D. Noe_, Mar 01 2013 *)

%Y Cf. A033496, A222562, A222597.

%K nonn

%O 1,1

%A _Jayanta Basu_, Mar 01 2013