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A139399 Number of steps to reach a cycle in Collatz problem. 8
0, 0, 5, 0, 3, 6, 14, 1, 17, 4, 12, 7, 7, 15, 15, 2, 10, 18, 18, 5, 5, 13, 13, 8, 21, 8, 109, 16, 16, 16, 104, 3, 24, 11, 11, 19, 19, 19, 32, 6, 107, 6, 27, 14, 14, 14, 102, 9, 22, 22, 22, 9, 9, 110, 110, 17, 30, 17, 30, 17, 17, 105, 105, 4, 25, 25, 25, 12, 12, 12, 100, 20, 113, 20 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

a(1)=a(2)=a(4)=0 as A006370(A006370(A006370(x)))=x for x=1,2,4 [corrected by Rémy Sigrist, Jun 28 2020];

a(n) = A006577(n) - 2 for n > 2 (if the conjecture holds).

For n>2: let L = a(n) mod 3, then A006460(n) = if L=0 then 4 else L. - Reinhard Zumkeller, Nov 17 2013

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Index entries for sequences related to 3x+1 (or Collatz) problem

Eric Weisstein's World of Mathematics, Collatz Problem

PROG

(Haskell)

a139399 = f 0 where

   f k x = if x `elem` [1, 2, 4] then k else f (k + 1) (a006370 x)

-- Reinhard Zumkeller, Nov 17 2013

CROSSREFS

Essentially the same sequence as A112695.

Cf. A006370, A006460.

Sequence in context: A197573 A019947 A193182 * A318525 A021669 A011511

Adjacent sequences:  A139396 A139397 A139398 * A139400 A139401 A139402

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Apr 18 2008

STATUS

approved

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Last modified May 16 01:53 EDT 2021. Contains 343937 sequences. (Running on oeis4.)