A067880 Numbers k such that phi(k) = phi(sigma(k)-k).

2, 4, 6, 10, 16, 28, 78, 114, 152, 165, 186, 222, 224, 238, 256, 402, 496, 654, 704, 738, 762, 834, 942, 1086, 1194, 1266, 1456, 1485, 1665, 1722, 1842, 1972, 2022, 2132, 2223, 2274, 2454, 2528, 2754, 2922, 2994, 3246, 3426, 3462, 3472, 3786, 4506, 4614

Offset: 1

Author

Benoit Cloitre, Mar 02 2002

Keywords

• easy
• nonn

Links

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

Crossrefs

Cf. A000010, A000203, A001065, A006872.

Programs

Mathematica

Select[Range[5000], EulerPhi[#] == EulerPhi[DivisorSigma[1, #] - #] &] (* Amiram Eldar, Apr 24 2022 *)