A362664 Numbers k with exactly two solutions x to the equation iphi(x) = k, where iphi is the infinitary totient function A091732.

1, 2, 3, 4, 10, 15, 20, 22, 28, 42, 44, 45, 46, 52, 54, 56, 58, 70, 78, 82, 92, 100, 102, 104, 106, 116, 130, 136, 140, 148, 162, 164, 166, 172, 174, 178, 184, 190, 196, 200, 204, 208, 212, 220, 222, 226, 228, 234, 238, 246, 250, 255, 260, 262, 268, 272, 282, 292, 296

Offset

1,2

Comments

Numbers k such that A362485(k) = 2.

There are no numbers k with a single solution to iphi(x) = k, because if iphi(x) = k, and A007814(x) is even, then 2*x is also a solution, i.e., iphi(2*x) = k.

Links

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

Mathematica

Select[Range[300], Length[invIPhi[#]] == 2 &] (* using the function invIPhi from A362484 *)

Crossrefs

Cf. A007814, A091732, A362484, A362485.

Similar sequences: A361969, A362185.

Sequence in context: A115195 A095384 A177084 * A115899 A183527 A085934

Adjacent sequences: A362661 A362662 A362663 * A362665 A362666 A362667

Keyword

nonn

Author

Amiram Eldar, Apr 29 2023

Status

approved