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A185589
Iterate the map in A006369 starting at 144.
20
144, 96, 64, 85, 113, 151, 201, 134, 179, 239, 319, 425, 567, 378, 252, 168, 112, 149, 199, 265, 353, 471, 314, 419, 559, 745, 993, 662, 883, 1177, 1569, 1046, 1395, 930, 620, 827, 1103, 1471, 1961, 2615, 3487, 4649, 6199, 8265, 5510, 7347, 4898, 6531, 4354, 5805, 3870, 2580, 1720, 2293, 3057, 2038, 2717, 3623, 4831
OFFSET
1,1
COMMENTS
Lagarias, page 270, appears to imply that this trajectory has period 12 and smallest element 144, which is not true.
REFERENCES
J. C. Lagarias, ed., The Ultimate Challenge: The 3x+1 Problem, Amer. Math. Soc., 2010; see page 270.
MATHEMATICA
f[n_] := If[Mod[n, 3] == 0, 2*n/3, Round[4*n/3]]; a[1] = 144; a[n_] := a[n] = f[a[n - 1]]; Table[a[n], {n, 1, 59}] (* Jean-François Alcover, Jun 10 2013 *)
SubstitutionSystem[{n_ :> Switch[Mod[n, 3], 0, 2n/3, 1, (4n - 1)/3, _, (4n + 1)/3]}, {144}, 60] // Flatten (* Jean-François Alcover, Mar 01 2019 *)
PROG
(Haskell)
a185589 n = a185589_list !! (n-1)
a185589_list = iterate a006369 144 -- Reinhard Zumkeller, Dec 31 2011
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Feb 04 2011
STATUS
approved