A377880 Nonprime cubefree numbers.
1, 4, 6, 9, 10, 12, 14, 15, 18, 20, 21, 22, 25, 26, 28, 30, 33, 34, 35, 36, 38, 39, 42, 44, 45, 46, 49, 50, 51, 52, 55, 57, 58, 60, 62, 63, 65, 66, 68, 69, 70, 74, 75, 76, 77, 78, 82, 84, 85, 86, 87, 90, 91, 92, 93, 94, 95, 98, 99, 100, 102, 105, 106, 110, 111
Offset: 1
Keywords
Programs
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Maple
q:= n-> not isprime(n) and andmap(i-> i[2]<3, ifactors(n)[2]): select(q, [$1..111])[]; # Alois P. Heinz, Nov 10 2024
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Mathematica
Select[Range[120], !PrimeQ[#] && Max[FactorInteger[#][[;; , 2]]] < 3 &] (* Amiram Eldar, Nov 10 2024 *)
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Python
from sympy import primepi, mobius, integer_nthroot def A377880(n): def f(x): return int(n+x+primepi(x)-sum(mobius(k)*(x//k**3) for k in range(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, Nov 13 2024