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A125711 In the "3x+1" problem, let 1 denote a halving step and 0 denote an x->3x+1 step. Then a(n) is obtained by writing the sequence of steps needed to reach 1 from 2n and reading it as a decimal number. 5
1, 3, 175, 7, 47, 431, 87791, 15, 743151, 111, 22255, 943, 751, 218863, 175087, 31, 5871, 1791727, 1431279, 239, 191, 55023, 44015, 1967, 11917039, 1775, 3515647479163389605506303638875119, 481007, 382703, 437231 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..30.

EXAMPLE

6 -> 3 -> 10 -> 5 -> 16 -> 8 -> 4 -> 2 -> 1, so a(3) is the decimal equivalent of 10101111, which is 175.

MATHEMATICA

f[x_] := If[EvenQ[x], x/2, 3x + 1]; g[n_] := FromDigits[Mod[Most[NestWhileList[f, 2n, # > 1 &]], 2, 1] - 1, 2]; Table[g[n], {n, 40}] (* Ray Chandler *)

CROSSREFS

Cf. A125710, A125626.

Sequence in context: A299304 A299462 A300105 * A268949 A113270 A091324

Adjacent sequences:  A125708 A125709 A125710 * A125712 A125713 A125714

KEYWORD

nonn,base

AUTHOR

N. J. A. Sloane, Feb 01 2007

EXTENSIONS

Extended by Ray Chandler, Feb 02 2007

STATUS

approved

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Last modified June 24 10:10 EDT 2019. Contains 324323 sequences. (Running on oeis4.)