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%I #1 Jan 12 2007 03:00:00
%S 3,4,4,7,7,8,5,18,9,32,11,77,25,10,6,36,29,18,17,12,28,14,23,45,73,55,
%T 91,16,17,39,7,36,40,114,87,100,93,34,54,64,15,55,171,80,57,72,42,108,
%U 24,12,97,68,31,159,88,10,41,50,23,117,63,61,8,55,72,45,68,24,18,211,57
%N Number of iterations needed before a previous value is reached in the Collatz variation: x_{i+1} = 3x_i+(2n+1) if x_i is odd or x_i/2 if x_i is even, with x_0 = 1.
%e a(1) = 4 because there are 4 steps to reach a previous value:
%e step 1: x = 3*1 +(2n+1) = 6
%e step 2: x = 6/2 = 3;
%e step 3: x = 3*3 +(2n+1) = 12
%e step 4: x = 12/2 = 6, which was the result of step 1
%Y Cf. A127142, A127143.
%K nonn
%O 0,1
%A Bryan Jacobs (bryanjj(AT)gmail.com), Jan 06 2007
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