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A217301 Numbers n such that gcd(n, phi(n)) = gcd(phi(n), sigma(n)) = gcd(sigma(n), n) = tau(n). 2

%I

%S 1,184,376,1336,1912,2104,2872,3064,3832,4024,4792,5176,5752,5944,

%T 6712,6904,7096,7864,8824,9784,10552,10936,11512,11896,12472,12664,

%U 12856,14584,14776,16312,16504,16696,17656,19192,19384,19576,20344,21304,21496,22644

%N Numbers n such that gcd(n, phi(n)) = gcd(phi(n), sigma(n)) = gcd(sigma(n), n) = tau(n).

%H Vincenzo Librandi, <a href="/A217301/b217301.txt">Table of n, a(n) for n = 1..1000</a>

%t Select[Range[20000], GCD[#, EulerPhi[#]] == GCD[EulerPhi[#], DivisorSigma[1, #]] == GCD[#, DivisorSigma[1, #]] == DivisorSigma[0, #] &] (* _Jean-Fran├žois Alcover_, Mar 18 2013 *)

%Y Cf. A069810.

%K nonn,easy

%O 1,2

%A _Jayanta Basu_, Mar 17 2013

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Last modified October 22 22:35 EDT 2021. Contains 348180 sequences. (Running on oeis4.)