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单词 IteratedTotientFunction
释义

iterated totient function


The iterated totient function ϕk(n) is ak in the recurrence relation a0=n and ai=ϕ(ai-1) for i>0, where ϕ(x) is Euler’s totient function.

After enough iterations, the function eventually hits 2 followed by an infiniteMathworldPlanetmath trail of ones. Ianucci et al define the “class” c of n as the integer such that ϕc(n)=2.

When the iterated totient function is summed thus:

i=1c+1ϕi(n)

it can be observed that just as 2x is a quasiperfect number when it comes to adding up proper divisors, it is also “quasiperfect” when adding up the iterated totient function. Quite unlike regularPlanetmathPlanetmath perfect numbers, 3x (which are obviously odd) are “perfect” when adding up the iterated totient.

References

  • 1 D. E. Ianucci, D. Moujie & G. L. Cohen, “On Perfect Totient Numbers” Journal of Integer Sequences, 6, 2003: 03.4.5
  • 2 R. K. Guy, Unsolved Problems in Number TheoryMathworldPlanetmathPlanetmath New York: Springer-Verlag 2004: B42
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更新时间:2025/5/4 15:02:40