A322028 - OEIS

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A322028

Number of distinct orders of primeness among the prime factors of n.

0, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 2, 1, 1, 2, 1, 1, 2, 1, 2, 2, 2, 1, 2, 1, 1, 1, 1, 1, 3, 1, 1, 2, 2, 2, 2, 1, 1, 2, 2, 1, 2, 1, 2, 2, 1, 1, 2, 1, 2, 1, 1, 1, 2, 2, 1, 2, 1, 1, 3, 1, 2, 2, 1, 2, 3, 1, 2, 2, 2, 1, 2, 1, 1, 2, 1, 2, 2, 1, 2, 1, 2, 1, 2, 2, 1, 2

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OFFSET

1,6

COMMENTS

The order of primeness (A078442) of a prime number p is the number of times one must apply A000720 to obtain a nonprime number.

LINKS

Alois P. Heinz, Table of n, a(n) for n = 1..65536

N. Fernandez, An order of primeness, F(p)

N. Fernandez, An order of primeness [cached copy, included at A006450 with permission of the author]

EXAMPLE

a(105) = 3 because the prime factors of 105 = 3*5*7 have 3 different orders of primeness, namely 2, 3, and 1 respectively.

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