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