A068502 Composite numbers k such that gcd(sigma(k), k) = gcd(k, phi(k)).

10, 12, 14, 22, 26, 34, 35, 38, 42, 44, 45, 46, 56, 58, 62, 65, 70, 74, 76, 77, 78, 82, 85, 86, 92, 94, 99, 105, 106, 114, 115, 118, 119, 122, 124, 130, 133, 134, 142, 143, 146, 154, 158, 161, 166, 168, 170, 172, 178, 184, 185, 186, 187, 188, 194, 195, 202, 206

Offset: 1

Author

Benoit Cloitre, Mar 11 2002

Keywords

• easy
• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000010, A000203, A009194, A009195.

Programs

Mathematica

Cases[Range[2, 206], n_ /; !PrimeQ[n] && GCD[Total[Divisors[n]], n] == GCD[n, EulerPhi[n]]] (* Jean-François Alcover, Mar 15 2011 *)
fQ[n_]:=!PrimeQ[n]&&GCD[Total[Divisors[n]],n] == GCD[n,EulerPhi[n]];Select[Range[2,206],fQ] (* Zak Seidov, Mar 15 2011 *)