A377711 Numbers that have a record number of (1+phi)-divisors (A061389).

1, 2, 6, 24, 30, 96, 120, 210, 480, 840, 1920, 2310, 3360, 9240, 13440, 30030, 36960, 120120, 147840, 332640, 480480, 1330560, 1921920, 4324320, 8168160, 17297280, 30750720, 32672640, 73513440, 155195040, 294053760, 522762240, 620780160, 1396755360, 2646483840

Offset: 1

Author

Amiram Eldar, Nov 04 2024

Keywords

• nonn

Comments

Indices of records in A061389.

The corresponding record values are 1, 2, 4, 6, 8, 10, 12, 16, 20, 24, 28, 32, 40, 48, 56, ... (see the link for more values).

Links

• Amiram Eldar, Table of n, a(n) for n = 1..231
• Amiram Eldar, Table of n, a(n), A363825(a(n)) for n = 1..231

Crossrefs

Cf. A061389, A307004.

Subsequence of A025487.

Programs

Mathematica

f[p_, e_] := EulerPhi[e] + 1; d[1] = 1; d[n_] := Times @@ f @@@ FactorInteger[n]; v = Cases[Import["https://oeis.org/A025487/b025487.txt", "Table"], {, }][[;; , 2]]; seq = {}; dm = 0; Do[If[(dk = d[v[[k]]]) > dm, dm = dk; AppendTo[seq, v[[k]]]], {k, 1, Length[v]}]; seq