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A092892
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Smallest starting value in a Collatz '3x+1' sequence such that the sequence contains exactly n halving steps.
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7
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1, 2, 4, 8, 5, 3, 6, 12, 24, 17, 11, 7, 14, 9, 18, 36, 25, 49, 33, 65, 43, 86, 57, 39, 78, 153, 105, 203, 135, 270, 185, 123, 246, 169, 329, 219, 159, 295, 569, 379, 283, 505, 377, 251, 167, 111, 222, 444, 297, 593, 395, 263, 175, 350, 233, 155, 103, 206, 137, 91, 182
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OFFSET
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0,2
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COMMENTS
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The graph of this sequence has features similar to those of A092893, but with the x-axis scaled by log(3)/log(2). - T. D. Noe, Apr 09 2007
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LINKS
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EXAMPLE
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a(5)=3 because the Collatz sequence 3,10,5,16,8,4,2,1 is the first sequence containing 5 halving steps.
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MATHEMATICA
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coll[n_]:= NestWhileList[If[EvenQ[#], #/2, 3#+1] &, n, #>1 &]; Table[i = 1; While[Count[coll[i], _?EvenQ] != n, i++]; i, {n, 0, 60}] (* Jayanta Basu, Jun 05 2013 *)
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PROG
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(Haskell)
import Data.List (elemIndex); import Data.Maybe (fromJust)
a092892 = (+ 1) . fromJust . (`elemIndex` a006666_list)
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CROSSREFS
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KEYWORD
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AUTHOR
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STATUS
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approved
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