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A358051
Squares k such that phi(k) is a cube.
0
1, 16, 1024, 2500, 5184, 50625, 65536, 160000, 331776, 810000, 3779136, 4194304, 4691556, 5345344, 7001316, 10240000, 16867449, 20820969, 21233664, 27060804, 36905625, 39062500, 51840000, 52200625, 228765625, 241864704, 268435456, 269879184, 300259584, 333135504
OFFSET
1,2
FORMULA
a(n) = A114076(n)^2. - Amiram Eldar, Oct 27 2022
MATHEMATICA
Select[Range[20000]^2, IntegerQ[Surd[EulerPhi[#], 3]] &] (* Amiram Eldar, Oct 27 2022 *)
PROG
(Python)
from sympy.ntheory.factor_ import totient
from gmpy2 import *
def isok(k):
if is_square(k):
j = isqrt(k)
a, b = iroot(totient(j) * j, 3)
return b
(PARI) isok(k) = issquare(k) && ispower(eulerphi(k), 3); \\ Michel Marcus, Oct 27 2022
CROSSREFS
Sequence in context: A070307 A159683 A197104 * A067490 A130036 A013735
KEYWORD
nonn
AUTHOR
Darío Clavijo, Oct 27 2022
STATUS
approved