OFFSET
0,3
LINKS
Eric Weisstein's World of Mathematics, Cubefree.
FORMULA
a(n) = Sum_{k=1..n} A004709(k)^3.
a(n) ~ c * n^4, where c = zeta(3)^3/4 = 0.4342252653... . - Amiram Eldar, Feb 20 2024
EXAMPLE
1^3 + 2^3 + 3^3 + 4^3 + 5^3 + 6^3 + 7^3 + 9^3 + 10^3 + 11^3 = 3844 = 2^2 * 31^2.
MATHEMATICA
cubeFreeQ[n_] := Max[FactorInteger[n][[;; , 2]]] < 3; Join[{0}, Accumulate[Select[Range[50], cubeFreeQ]^3]] (* Amiram Eldar, Feb 20 2024 *)
KEYWORD
easy,nonn
AUTHOR
Jonathan Vos Post, Nov 20 2005
STATUS
approved