A333103 Quasiperfect cototient numbers: numbers k such that the sum of the iterated cototient function of k is equal to k+1.

6, 14, 62, 254, 16382, 78585, 87465, 262142, 1048574

Offset: 1

Author

Amiram Eldar, Mar 07 2020

Keywords

• nonn
• more

Comments

If m is in A050475 then 2^m - 2 is a term.

3*10^8 < a(10) <= 4294967292.

Examples

			6 is a term since A051953(6) = 4, A051953(4) = 2, A051953(2) = 1, and 4 + 2 + 1 = 7 = 6 + 1.
		

Links

• Wikipedia, Perfect totient number.
• Wikipedia, Quasiperfect number.

Crossrefs

Cf. A050475, A051953, A082897, A286067, A330273.

Programs

Mathematica

cot[n_] := n - EulerPhi[n]; s[n_] := Plus @@ FixedPointList[cot, n]; Select[Range[10^5], s[#] == 2*# + 1 &]