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A008884
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3x+1 sequence starting at 27.
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7
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27, 82, 41, 124, 62, 31, 94, 47, 142, 71, 214, 107, 322, 161, 484, 242, 121, 364, 182, 91, 274, 137, 412, 206, 103, 310, 155, 466, 233, 700, 350, 175, 526, 263, 790, 395, 1186, 593, 1780, 890, 445, 1336, 668, 334, 167, 502, 251, 754, 377, 1132, 566, 283, 850, 425, 1276, 638, 319, 958, 479, 1438, 719, 2158, 1079
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,1
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COMMENTS
| 27=A060412(4); a(A006577(27))=a(111)=1; a(n)=A161021(n+59) for n with 103<=n<=111. [From Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Jun 03 2009]
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REFERENCES
| R. K. Guy, Unsolved Problems in Number Theory, E16.
H.-O. Peitgen et al., Chaos and Fractals, Springer, p. 33.
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LINKS
| T. D. Noe, Table of n, a(n) for n=0..111
Index entries for sequences related to 3x+1 (or Collatz) problem
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FORMULA
| a(0) = 27, a(n) = 3*a(n-1)+1 if a(n-1) is odd, a(n) = a(n-1)/2 if a(n-1) is even. [From Vincenzo Librandi, Dec 24 2010; corrected by Klaus Brockhaus, Dec 25 2010]
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MAPLE
| f := proc(n) option remember; if n = 0 then 27; elif f(n-1) mod 2 = 0 then f(n-1)/2 else 3*f(n-1)+1; fi; end;
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MATHEMATICA
| NestList[If[EvenQ[#], #/2, 3#+1]&, 27, 70] (* From Harvey P. Dale, June 30 2011 *)
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PROG
| (MAGMA) [ n eq 1 select 27 else IsOdd(Self(n-1)) select 3*Self(n-1)+1 else Self(n-1) div 2: n in [1..70] ]; // Klaus Brockhaus, Dec 25 2010
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CROSSREFS
| A161022, A161023. [From Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Jun 03 2009]
Sequence in context: A129254 A034033 A057609 * A031455 A045004 A042432
Adjacent sequences: A008881 A008882 A008883 * A008885 A008886 A008887
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KEYWORD
| nonn,nice
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| More terms from Larry Reeves (larryr(AT)acm.org), Apr 27 2001
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