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

1,1

Comments

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

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

Links

Table of n, a(n) for n=1..9.

Wikipedia, Perfect totient number.

Wikipedia, Quasiperfect number.

Example

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

Mathematica

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

Crossrefs

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

Sequence in context: A032404 A059954 A252541 * A139257 A056842 A182752

Adjacent sequences: A333100 A333101 A333102 * A333104 A333105 A333106

Keyword

nonn,more

Author

Amiram Eldar, Mar 07 2020

Status

approved