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a(n) is the least k such that A340873(k) = n.
3

%I #8 Feb 09 2021 11:01:45

%S 1,2,4,3,6,12,5,10,20,13,25,9,17,34,29,57,114,41,81,49,97,33,65,129,

%T 113,225,449,169,337,201,401,801,285,545,489,925,1833,641,1281,769,

%U 1537,513,1025,2049,1793,3585,1473,2689,1665,3201,6401,2557,4381,3753,7505

%N a(n) is the least k such that A340873(k) = n.

%H Rémy Sigrist, <a href="/A341194/a341194.png">Illustration of initial terms</a>

%H Rémy Sigrist, <a href="/A341194/a341194.txt">C program for A341194</a>

%H <a href="/index/3#3x1">Index entries for sequences related to 3x+1 (or Collatz) problem</a>

%F a(n) <= 2^n.

%F a(n+1) <= 2*a(n).

%e See Illustration in Links section.

%o (C) See Links section.

%Y Cf. A033491, A340873.

%K nonn,base

%O 0,2

%A _Rémy Sigrist_, Feb 06 2021