OFFSET

1,2

COMMENTS

This sequence has similarities with A289280.

Each power of a prime appears in the sequence.

Each prime number appears once in the sequence.

LINKS

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

FORMULA

a(n) >= n with equality iff n belongs to A000961.

EXAMPLE

For n = 42:

- 42 has 3 primes factors: 2, 3 and 7,

- the least power of 2 >= 42 is 64,

- the least power of 3 >= 42 is 81,

- the least power of 7 >= 42 is 49,

- hence a(42) = 49.

PROG

(PARI) a(n) = my (pp=factor(n)[, 1]~); if (#pp <= 1, n, vecmin(apply(p -> p^(1+logint(n, p)), pp)))

CROSSREFS

KEYWORD

nonn

AUTHOR

Rémy Sigrist, Jan 07 2019

STATUS

approved