OFFSET
1,2
COMMENTS
a(n) depends only on prime signature of n (cf. A025487).
LINKS
FORMULA
EXAMPLE
For n = 30 = 2 * 3 * 5, there are three unitary prime factors, while A003557(30) = 1, which terminates the recursion, thus a(30) = prime(3) = 5.
For n = 60060 = 2^2 * 3 * 5 * 7 * 11 * 13, there are 5 unitary prime factors, while in A003557(60060) = 2 there are one, thus a(60060) = prime(5) * prime(1) = 11 * 2 = 22.
The number 1260 = 2^2*3^2*5*7 has prime exponents (2,2,1,1) so its prime shadow is prime(2)*prime(2)*prime(1)*prime(1) = 36. Next, 36 = 2^2*3^2 has prime exponents (2,2) so its prime shadow is prime(2)*prime(2) = 9. In fact, the term a(1260) = 9 is the first appearance of 9 in the sequence. - Gus Wiseman, Apr 28 2022
PROG
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Oct 29 2019
EXTENSIONS
Added Gus Wiseman's new name to the front of the definition. - Antti Karttunen, Apr 27 2022
STATUS
approved