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Number of halving and tripling steps for 10^n to reach 1 in '3x+1' problem.
1

%I #11 Jun 25 2021 12:09:30

%S 6,25,111,29,128,152,145,107,100,124,347,146,289,194,275,255,235,303,

%T 340,470,357,324,454,266,564,433,470,331,492,467,584,515,614,550,711,

%U 497,653,1039,577,694,749,755,779,666,752,913,769,754,724,691,883,827,683

%N Number of halving and tripling steps for 10^n to reach 1 in '3x+1' problem.

%H Michael S. Branicky, <a href="/A094669/b094669.txt">Table of n, a(n) for n = 1..10000</a>

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

%F a(n) = A006577(A011557(n)). - _Michel Marcus_, Jun 25 2021

%o (Python)

%o def f(x): return x//2 if x%2 == 0 else 3*x + 1

%o def a(n):

%o i, c = 10**n, 0

%o while i != 1: i, c = f(i), c+1

%o return c

%o print([a(n) for n in range(1, 54)]) # _Michael S. Branicky_, Jun 25 2021

%Y Cf. A006577, A011557.

%K easy,nonn

%O 1,1

%A _Jason Earls_, Jun 07 2004

%E a(53) and beyond from _Michael S. Branicky_, Jun 25 2021