OFFSET
1,1
COMMENTS
2^3=8, 3^3=27, 4^3=64=2^6 is not in the sequence, 5^3=125, 6^3=216, ...
MATHEMATICA
Select[Range[2, 100], GCD@@Last/@FactorInteger@#==1&]^3
PROG
(Python)
from sympy import mobius, integer_nthroot
def A153147(n):
def f(x): return int(n+1-sum(mobius(k)*(integer_nthroot(x, k)[0]-1) for k in range(2, x.bit_length())))
m, k = n, f(n)
while m != k: m, k = k, f(k)
return m**3
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladimir Joseph Stephan Orlovsky, Dec 19 2008
EXTENSIONS
Edited by Ray Chandler, Dec 22 2008
STATUS
approved