OFFSET
1,2
COMMENTS
Also numbers with no distinct prime numbers in their prime tower factorization (see A182318 for the definition of the prime tower factorization of a number).
LINKS
Rémy Sigrist, Table of n, a(n) for n = 1..10000
Wikipedia, Tetration
EXAMPLE
16 = 2^^3 is in the sequence.
CROSSREFS
KEYWORD
nonn
AUTHOR
Rémy Sigrist, Apr 01 2017
STATUS
approved