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

1,2

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, ...

Links

Table of n, a(n) for n=1..30.

Example

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.

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

Crossrefs

Cf. A000010, A102190.

Sequence in context: A274305 A317013 A369075 * A295864 A255506 A095717

Adjacent sequences: A328854 A328855 A328856 * A328858 A328859 A328860

Keyword

nonn

Author

Amiram Eldar, Oct 28 2019

Status

approved