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 A193688 Number of steps to reach 1 in Collatz (3x+1) problem starting with 2^n - 1. 4
 0, 7, 16, 17, 106, 107, 46, 47, 61, 62, 156, 157, 158, 159, 129, 130, 224, 225, 177, 178, 303, 304, 473, 474, 444, 445, 384, 385, 448, 449, 450, 451, 527, 528, 529, 530, 531, 532, 533, 534, 535, 536, 586, 587, 588, 589, 590, 591, 592, 593, 594, 595, 852 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Arkadiusz Wesolowski, Table of n, a(n) for n = 1..10000 Eric Weisstein's World of Mathematics, Collatz Problem FORMULA For larger n, a(n) ~ 13.5*n. MATHEMATICA Table[Length[NestWhileList[If[OddQ@#, 3 # + 1, #/2] &, 2^n - 1, # > 1 &]] - 1, {n, 60}] (* Arkadiusz Wesolowski, Sep 16 2011 *) PROG (Python) for i in range(1, 100):     n = 2**i - 1     x = n     c = 0     while x != 1:         c = c + 1         if (x & 1) == 0:             x = x//2         else:             x = 3*x + 1     print(c) # David Rabahy, Sep 18 2017 CROSSREFS Cf. A006577, A179118 (starting with 2^n+1). Sequence in context: A070417 A101681 A067776 * A132348 A177763 A101073 Adjacent sequences:  A193685 A193686 A193687 * A193689 A193690 A193691 KEYWORD nonn AUTHOR Arkadiusz Wesolowski, Aug 02 2011 STATUS approved

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