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A036452
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d(d(d(d(n)))), the 4th iterate of number-of-divisors function with initial value of n.
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8
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1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| The iterated d function rapidly converges to fixed point 2. For k=4 the first n for which a(n)>2 is 60.
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LINKS
| Enrique Pérez Herrero, Table of n, a(n) for n = 1..2000
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FORMULA
| a(n) = d(d(d(d(n)))).
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EXAMPLE
| E.g. n=96 and its successive iterates are 12,6,4,3 and 2. The 4th term is a(96)=3.
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MATHEMATICA
| f[n_]:=DivisorSigma[0, n]; Table[Nest[f, n, 4], {n, 100}] [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Mar 10 2010]
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CROSSREFS
| Cf. A000005, A010553, A036450, A036453.
Sequence in context: A040000 A055642 A138902 * A102572 A098391 A071702
Adjacent sequences: A036449 A036450 A036451 * A036453 A036454 A036455
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KEYWORD
| nonn
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AUTHOR
| Labos E. (labos(AT)ana.sote.hu)
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