OFFSET
1,1
COMMENTS
LINKS
MATHEMATICA
Select[Range[600], Max[FactorInteger[#][[;; , 2]]] == 3 &]
PROG
(PARI) is(k) = k > 1 && vecmax(factor(k)[, 2]) == 3;
(Python)
from sympy import mobius, integer_nthroot
def A375072(n):
def f(x): return n+x-sum(mobius(k)*(x//k**4-x//k**3) for k in range(1, integer_nthroot(x, 4)[0]+1))+sum(mobius(k)*(x//k**3) for k in range(integer_nthroot(x, 4)[0]+1, integer_nthroot(x, 3)[0]+1))
m, k = n, f(n)
while m != k:
m, k = k, f(k)
return m # Chai Wah Wu, Aug 05 2024
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Amiram Eldar, Jul 29 2024
STATUS
approved