

A125710


In the "3x+1" problem, let 0 denote a halving step and 1 denote an x>3x+1 step. Then a(n) is obtained by writing the sequence of steps needed to reach 1 from 2n+1 and reading it as a decimal number.


5



4, 80, 16, 43280, 305424, 10512, 272, 87056, 2320, 665872, 64, 21520, 4860176, 1676649379371438023024192690344976, 141584, 54056611079304389108412587463696, 38414608, 5136, 1091856, 11358841104
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OFFSET

0,1


LINKS



EXAMPLE

7 > 22 > 11 > 34 > 17 > 52 > 26 > 13 > 40 > 20 > 10 > 5 > 16 > 8 > 4 > 2 > 1, so a(3) is the
decimal equivalent of 1010100100010000, which is 43280.


MATHEMATICA

f[x_] := If[EvenQ[x], x/2, 3x + 1]; g[n_] := FromDigits[Mod[Most[NestWhileList[f, 2n + 1, # > 1 &, {2, 1}]], 2], 2]; Table[g[n], {n, 0, 30}] (* Ray Chandler, Feb 02 2007 *)


CROSSREFS



KEYWORD

nonn,base


AUTHOR



EXTENSIONS



STATUS

approved



