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A028394
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Iterate the map in A006369 starting at 8.
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8
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8, 11, 15, 10, 13, 17, 23, 31, 41, 55, 73, 97, 129, 86, 115, 153, 102, 68, 91, 121, 161, 215, 287, 383, 511, 681, 454, 605, 807, 538, 717, 478, 637, 849, 566, 755, 1007, 1343, 1791, 1194, 796, 1061, 1415
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,1
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COMMENTS
| It is an unsolved problem to determine if this sequence is bounded or unbounded.
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REFERENCES
| D. Gale, Tracking the Automatic Ant and Other Mathematical Explorations, A Collection of Mathematical Entertainments Columns from The Mathematical Intelligencer, Springer, 1998; see p. 16. [From N. J. A. Sloane, Jul 14 2009]
J. C. Lagarias, ed., The Ultimate Challenge: The 3x+1 Problem, Amer. Math. Soc., 2010; see page 270.
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LINKS
| T. D. Noe, Table of n, a(n) for n=0..1000
J. C. Lagarias, The 3x+1 problem and its generalizations, Amer. Math. Monthly, 92 (1985), 3-23.
Index entries for sequences related to 3x+1 (or Collatz) problem
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FORMULA
| The map is: n -> if n mod 3 = 0 then 2*n/3 elif n mod 3 = 1 then (4*n-1)/3 else (4*n+1)/3.
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MAPLE
| G := proc(n) option remember; if n = 0 then 8 elif 4*G(n-1) mod 3 = 0 then 2*G(n-1)/3 else round(4*G(n-1)/3); fi; end; [ seq(G(i), i=0..80) ];
f:=proc(N) local n;
if N mod 3 = 0 then 2*(N/3);
elif N mod 3 = 2 then 4*((N+1)/3)-1; else
4*((N+2)/3)-3; fi; end; (from N. J. A. Sloane, Feb 04 2011]
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PROG
| (Haskell)
a028394 n = a028394_list !! n
a028394_list = iterate a006369 8 -- Reinhard Zumkeller, Dec 31 2011
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CROSSREFS
| Cf. A006369, A028396, A094328, A094329, A185589, A185590.
Sequence in context: A096679 A101573 A029629 * A188199 A078117 A032423
Adjacent sequences: A028391 A028392 A028393 * A028395 A028396 A028397
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KEYWORD
| nonn
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AUTHOR
| J. H. Conway (conway(AT)math.princeton.edu)
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