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A338669 The prime tower factorization of a(n) is obtained by replacing the rightmost prime number by 1 in the prime tower factorization of n; a(1) = 1. 2
1, 1, 1, 2, 1, 2, 1, 2, 3, 2, 1, 4, 1, 2, 3, 4, 1, 6, 1, 4, 3, 2, 1, 8, 5, 2, 3, 4, 1, 6, 1, 2, 3, 2, 5, 12, 1, 2, 3, 8, 1, 6, 1, 4, 9, 2, 1, 16, 7, 10, 3, 4, 1, 6, 5, 8, 3, 2, 1, 12, 1, 2, 9, 4, 5, 6, 1, 4, 3, 10, 1, 24, 1, 2, 15, 4, 7, 6, 1, 16, 9, 2, 1, 12 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

The prime tower factorization of a number is defined in A182318.

Sequence A338668 gives the rightmost prime number.

LINKS

Rémy Sigrist, Table of n, a(n) for n = 1..10000

Rémy Sigrist, Illustration of initial terms

FORMULA

a(n) = 1 iff n = 1 or n is a prime number.

A106490(a(n)) = 1 + A106490(n) for any n > 1.

a^k(n) = 1 for k = A106490(n) (where a^k denotes the k-th iterate of a).

EXAMPLE

See Links section.

PROG

(PARI) a(n) = { if (n==1, 1, my (f=factor(n), w=#f~, p=f[w, 1], e=f[w, 2]); if (e==1, n/p, n*p^(a(e)-e))) }

CROSSREFS

Cf. A106490, A182318, A338668.

Sequence in context: A034880 A257977 A070966 * A219254 A072504 A072499

Adjacent sequences:  A338666 A338667 A338668 * A338670 A338672 A338673

KEYWORD

nonn

AUTHOR

Rémy Sigrist, Apr 23 2021

STATUS

approved

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Last modified June 21 16:32 EDT 2021. Contains 345365 sequences. (Running on oeis4.)