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Composite numbers k such that gcd(sigma(k), k) = gcd(k, phi(k)).
1

%I #18 May 14 2022 11:30:24

%S 10,12,14,22,26,34,35,38,42,44,45,46,56,58,62,65,70,74,76,77,78,82,85,

%T 86,92,94,99,105,106,114,115,118,119,122,124,130,133,134,142,143,146,

%U 154,158,161,166,168,170,172,178,184,185,186,187,188,194,195,202,206

%N Composite numbers k such that gcd(sigma(k), k) = gcd(k, phi(k)).

%H Amiram Eldar, <a href="/A068502/b068502.txt">Table of n, a(n) for n = 1..10000</a>

%t Cases[Range[2, 206], n_ /; !PrimeQ[n] && GCD[Total[Divisors[n]], n] == GCD[n, EulerPhi[n]]] (* _Jean-François Alcover_, Mar 15 2011 *)

%t fQ[n_]:=!PrimeQ[n]&&GCD[Total[Divisors[n]],n] == GCD[n,EulerPhi[n]];Select[Range[2,206],fQ] (* _Zak Seidov_, Mar 15 2011 *)

%Y Cf. A000010, A000203, A009194, A009195.

%K easy,nonn

%O 1,1

%A _Benoit Cloitre_, Mar 11 2002