OFFSET
1,6
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..65537
FORMULA
EXAMPLE
a(12) = 12 because 12 has 6 divisors {1, 2, 3, 4, 6, 12} among which 3 are proper unitary {1, 3, 4} and 1*3*4 = 12.
MAPLE
with(numtheory):
a:= n-> mul(d, d=select(x-> igcd(x, n/x)=1, divisors(n) minus {n})):
seq(a(n), n=1..80); # Alois P. Heinz, Aug 03 2017
MATHEMATICA
Table[Product[d, {d, Select[Divisors[n], GCD[#, n/#] == 1 &]}]/n, {n, 80}]
Table[n^(2^(PrimeNu[n] - 1) - 1), {n, 80}]
PROG
(Python)
from sympy import divisors, gcd, prod
def a(n): return prod(d for d in divisors(n) if gcd(d, n//d) == 1)//n
print([a(n) for n in range(1, 51)]) # Indranil Ghosh, Aug 04 2017
(PARI) A290480(n) = if(1==n, n, n^(2^(omega(n)-1)-1)); \\ Antti Karttunen, Aug 06 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Aug 03 2017
STATUS
approved