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%I #11 Jan 11 2017 07:48:49
%S 2,3,2,1,4,1,2,2,3,1,2,2,4,1,2,3,3,4,2,2,6,1,4,3,3,1,2,2,4,3,2,4,6,1,
%T 2,5,5,1,2,3,3,7,8,2,4,1,2,4,3,4,6,2,6,3,2,3,3,1,2,4,4,1,17,5,6,7,2,2,
%U 5,3,2,6,5,1,2,2,4,3,4,4,3,1,6,8,8,1,2,3,3,5,2,2,6,1,15,5,3,4,2,5
%N Number of steps required to reach the first prime when starting from n in the Collatz (or '3x+1') problem.
%C If n=p*2^k, where k>0 and p is some prime then a(n)=k.
%C If n is odd then a(n)=a(3n+1)+1.
%C If n is even then a(n)=1 or a(n)=a(n/2)+1.
%C If n is composite then a(n)=A274472(n).
%H Dmitry Kamenetsky, <a href="/A280929/b280929.txt">Table of n, a(n) for n = 1..10000</a>
%e The Collatz iteration for 33 is 100, 50, 25, 76, 38, 19, 58, 29, ... 1. The first prime (19) is reached after 6 steps, so a(33)=6.
%Y Cf. A006577, A274472.
%K nonn
%O 1,1
%A _Dmitry Kamenetsky_, Jan 11 2017
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