OFFSET
1,1
COMMENTS
10^70 < a(17) <= 842075173279428103504117746722346581987825143261978794674517195307859044272000. - Max Alekseyev, Oct 07 2023
EXAMPLE
MATHEMATICA
a[n_] := Module[{k=2}, While[!IntegerQ[Surd[DivisorSigma[1, k]*EulerPhi[k], n]], k++]; k]; Array[a, 1, 5]
PROG
(PARI) a(n) = {my(k=2); while (!ispower(sigma(k)*eulerphi(k), n), k++); k; } \\ Michel Marcus, Mar 06 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Amiram Eldar, Mar 06 2019
EXTENSIONS
a(8) from Giovanni Resta, Mar 06 2019
a(9)-a(13) from Daniel Suteu confirmed, a(14)-a(16) added by Max Alekseyev, Oct 06 2023
STATUS
approved