A212639 - OEIS

A212639

Number of prime factors of A181800(n) (n-th powerful number that is the first integer of its prime signature), counted with multiplicity.

0, 2, 3, 4, 5, 4, 6, 5, 7, 6, 6, 8, 7, 7, 9, 8, 8, 6, 10, 9, 8, 9, 7, 11, 10, 9, 10, 8, 12, 11, 10, 8, 11, 9, 10, 13, 12, 11, 9, 12, 10, 11, 14, 13, 12, 10, 9, 13, 11, 12, 10, 15, 14, 13, 11, 8, 12, 10, 14, 12, 13, 11, 16, 15, 14, 12, 9, 13, 11, 15, 13, 14, 12

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OFFSET

1,2

COMMENTS

Every nonnegative integer n appears A002865(n) times.

LINKS

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

Will Nicholes, List of prime signatures

FORMULA

a(n) = A001222(A181800(n)).

EXAMPLE

72 (2^3*3^2, or 2*2*2*3*3) has a total of 5 prime factors when repetitions are counted. Since 72 = A181800(8), a(8) = 5.