A328857 Numbers with a record number of divisors that have the same value of the Euler totient function (A000010).

1, 2, 12, 120, 240, 2520, 10920, 21840, 32760, 65520, 600600, 900900, 1801800, 3603600, 4455360, 8910720, 17821440, 46060560, 69090840, 92121120, 126977760, 138181680, 245044800, 414545040, 490089600, 507911040, 1015822080, 1266665400, 1523733120, 2533330800

Offset: 1

Author

Amiram Eldar, Oct 28 2019

Keywords

• nonn

Comments

The corresponding record values are 1, 2, 3, 4, 5, 7, 8, 9, 10, 11, 13, 14, 16, 17, 18, 20, 21, 23, 24, 25, 26, 27, 29, 30, 31, 32, 33, 34, 35, 36, ...

Examples

			2 has 2 divisors with the same value of phi: phi(1) = phi(2) = 1.
12 has 3 divisors with the same value of phi: phi(3) = phi(4) = phi(6) = 2.
		

Crossrefs

Cf. A000010, A102190.

Programs

Mathematica

f[n_] := Max[Tally[EulerPhi /@ Divisors[n]][[;; , 2]]]; fm = 0; s = {}; Do[f1 = f[n]; If[f1 > fm, fm = f1; AppendTo[s, n]], {n, 1, 10^6}]; s