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A185590
Iterate the map in A006369 starting at 44.
20
44, 59, 79, 105, 70, 93, 62, 83, 111, 74, 99, 66, 44, 59, 79, 105, 70, 93, 62, 83, 111, 74, 99, 66, 44, 59, 79, 105, 70, 93, 62, 83, 111, 74, 99, 66, 44, 59, 79, 105, 70, 93, 62, 83, 111, 74, 99, 66, 44, 59, 79, 105, 70, 93, 62, 83, 111, 74, 99, 66, 44, 59, 79, 105, 70, 93, 62, 83, 111, 74, 99, 66, 44
OFFSET
1,1
COMMENTS
Periodic with period length 12.
REFERENCES
A. O. L. Atkin, Comment on Problem 63-13, SIAM Rev., 8 (1966), 234-236.
J. C. Lagarias, ed., The Ultimate Challenge: The 3x+1 Problem, Amer. Math. Soc., 2010; see page 270. (beware of typo: Lagarias says the orbit of 144 (not 44) has period 12.)
MATHEMATICA
f[n_] := If[Mod[n, 3] == 0, 2*n/3, Round[4*n/3]]; a[1] = 44; a[n_] := a[n] = f[a[n - 1]]; Table[a[n], {n, 1, 73}] (* Jean-François Alcover, Jun 10 2013 *)
PROG
(Haskell)
a185590 n = a185590_list !! (n-1)
a185590_list = iterate a006369 44 -- Reinhard Zumkeller, Dec 31 2011
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Feb 04 2011
STATUS
approved