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A062056
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Numbers with 6 odd integers in their Collatz (or 3x+1) trajectory.
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8
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7, 14, 15, 28, 29, 30, 56, 58, 60, 61, 112, 116, 117, 120, 122, 224, 232, 234, 240, 241, 244, 245, 267, 448, 464, 468, 469, 480, 482, 483, 488, 490, 497, 534, 535, 537, 896, 928, 936, 938, 960, 964, 965, 966, 976, 980, 981, 985, 994, 995, 1068, 1069, 1070, 1073
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OFFSET
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1,1
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COMMENTS
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The Collatz (or 3x+1) function is f(x) = x/2 if x is even, 3x+1 if x is odd.
The Collatz trajectory of n is obtained by applying f repeatedly to n until 1 is reached.
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REFERENCES
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J. Shallit and D. Wilson, The "3x+1" Problem and Finite Automata, Bulletin of the EATCS #46 (1992) pp. 182-185.
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LINKS
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EXAMPLE
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The Collatz trajectory of 7 is (7, 22, 11, 34, 17, 52, 26, 13, 40, 20, 10, 5, 16, 8, 4, 2, 1), which contains 6 odd integers.
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MATHEMATICA
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Collatz[n_] := NestWhileList[If[EvenQ[#], #/2, 3 # + 1] &, n, # > 1 &]; countOdd[lst_] := Length[Select[lst, OddQ]]; Select[Range[1000], countOdd[Collatz[#]] == 6 &] (* T. D. Noe, Dec 03 2012 *)
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PROG
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(Haskell)
import Data.List (elemIndices)
a062056 n = a062056_list !! (n-1)
a062056_list = map (+ 1) $ elemIndices 6 a078719_list
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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