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A153147
a(n) = A007916(n)^3.
5
8, 27, 125, 216, 343, 1000, 1331, 1728, 2197, 2744, 3375, 4913, 5832, 6859, 8000, 9261, 10648, 12167, 13824, 17576, 21952, 24389, 27000, 29791, 35937, 39304, 42875, 50653, 54872, 59319, 64000, 68921, 74088, 79507, 85184, 91125, 97336, 103823
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
KEYWORD
nonn
AUTHOR
EXTENSIONS
Edited by Ray Chandler, Dec 22 2008
STATUS
approved