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A070167 a(n) is the smallest starting value that produces a Collatz sequence in which n occurs. 7
1, 2, 3, 3, 3, 6, 7, 3, 9, 3, 7, 12, 7, 9, 15, 3, 7, 18, 19, 7, 21, 7, 15, 24, 25, 7, 27, 9, 19, 30, 27, 21, 33, 7, 15, 36, 37, 25, 39, 7, 27, 42, 43, 19, 45, 15, 27, 48, 43, 33, 51, 7, 15, 54, 55, 37, 57, 19, 39, 60, 27, 27, 63, 21, 43, 66, 39, 45, 69, 15, 27, 72, 73, 43, 75, 25 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(n) <= n. - Robert G. Wilson v, Jan 14 2015

LINKS

T. D. Noe, Table of n, a(n) for n=1..10000

Eric Weisstein's World of Mathematics, Collatz Sequence

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

MATHEMATICA

Collatz[n_] := NestWhileList[If[EvenQ[#], #/2, 3 # + 1] &, n, # > 1 &]; nn = 100; t = Table[0, {nn}]; n = 0; zeros = nn; While[zeros > 0, n++; c = Collatz[n]; Do[If[i <= nn && t[[i]] == 0, t[[i]] = n; zeros--], {i, c}]]; t (* T. D. Noe, Dec 03 2012 *)

PROG

(Haskell)

import Data.List (findIndex)

import Data.Maybe (fromJust)

a070167 n = fromJust (findIndex (elem n) a070165_tabf) + 1

-- Reinhard Zumkeller, Jan 02 2013

CROSSREFS

Cf. A006667, A070165.

Cf. A010120, A054646.

Sequence in context: A049982 A245642 A289559 * A168113 A170895 A141479

Adjacent sequences:  A070164 A070165 A070166 * A070168 A070169 A070170

KEYWORD

nonn

AUTHOR

Eric W. Weisstein, Apr 23 2002

STATUS

approved

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Last modified January 22 04:27 EST 2020. Contains 331133 sequences. (Running on oeis4.)