A333870 - OEIS

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A333870

The number of iterations of the absolute Möbius divisor function (A173557) required to reach from n to 1.

0, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 2, 1, 2, 2, 3, 2, 3, 3, 4, 2, 2, 3, 2, 3, 4, 2, 3, 1, 3, 2, 3, 2, 3, 3, 3, 2, 3, 3, 4, 3, 2, 4, 5, 2, 3, 2, 2, 3, 4, 2, 3, 3, 3, 4, 5, 2, 3, 3, 3, 1, 3, 3, 4, 2, 4, 3, 4, 2, 3, 3, 2, 3, 3, 3, 4, 2, 2, 3, 4, 3, 2, 4, 4

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OFFSET

1,3

COMMENTS

Apparently, the least number that reaches 1 after k iterations is A082449(k-1) (checked numerically for 1 <= k <= 17).

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000

Daeyeoul Kim, Umit Sarp, and Sebahattin Ikikardes, Iterating the Sum of Möbius Divisor Function and Euler Totient Function, Mathematics, Vol. 7, No. 11 (2019), pp. 1083-1094.

EXAMPLE

a(3) = 2 since there are 2 iterations from 3 to 1: A173557(3) = 2 and A173557(2) = 1.

MATHEMATICA

f[p_, e_] := p - 1; u[1] = 1; u[n_] := Times @@ (f @@@ FactorInteger[n]); a[n_] := Length @ FixedPointList[u, n] - 2; Array[a, 100]

CROSSREFS

Cf. A003434, A082449, A173557.

Sequence in context: A104232 A072086 A180094 * A354914 A366927 A103748

Adjacent sequences: A333867 A333868 A333869 * A333871 A333872 A333873

KEYWORD

nonn

AUTHOR

Amiram Eldar, Apr 08 2020

STATUS

approved