OFFSET
1,3
COMMENTS
FORMULA
a(n) = A000010(n)^3.
From Amiram Eldar, Jan 06 2023: (Start)
Multiplicative with a(p^e) = (p-1)^3*p^(3*e-3).
Sum_{k=1..n} a(k) ~ c * n^4, where c = (1/4) * Product_{p prime}(1 - 3/p^2 + 3/p^3 - 1/p^4) = 0.08429696844... .
Sum_{k>=1} 1/a(k) = Product_{p prime} (1 + p^3/((p-1)^3*(p^3-1))) = 2.47619474816... (A335818). (End)
EXAMPLE
a(9) = A000010(9)^3 = 216.
MATHEMATICA
a[n_] := EulerPhi[n]^3; Array[a, 100] (* Amiram Eldar, Jan 06 2023 *)
PROG
(Magma) [(EulerPhi(n))^3: n in [1..180]];
(PARI) a(n) = eulerphi(n)^3;
CROSSREFS
KEYWORD
nonn,easy,mult
AUTHOR
Param Mayurkumar Parekh and Paavan Mayurkumar Parekh, Nov 28 2022
STATUS
approved