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A116007

Numbers k such that k + sigma(k) + phi(k) is a fourth power.

81, 18904, 176705, 204576, 534160, 1362561, 1366633, 1698256, 1866768, 2034576, 2523024, 2909656, 3380856, 7217649, 9439473, 9454609, 11197696, 12866040, 29508673, 32363424, 34142545, 34682089, 46426160, 46448824, 53445456, 57807984, 58298881, 81378529, 98156353

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..108

EXAMPLE

81 + sigma(81) + phi(81) = 4^4.

MATHEMATICA

Select[Range[2*10^6], IntegerQ[Surd[# + DivisorSigma[1, #] + EulerPhi[#], 4]] &] (* Amiram Eldar, Dec 15 2023 *)

PROG

(PARI) isok(n) = ispower(n + sigma(n) + eulerphi(n), 4); \\ Michel Marcus, Jan 25 2014

CROSSREFS