A348198 Terms of A326835 having more divisors than any smaller term.

1, 3, 9, 15, 45, 105, 225, 405, 495, 1155, 3675, 4455, 8085, 19635, 62475, 75735, 137445, 373065, 1187025, 1741905, 2611455, 8580495, 27301575, 50515245, 60063465, 248834355, 1021078905, 2374216515, 2822982855, 11695214685, 47990708535

Offset

1,2

Comments

All the terms are odd since all the terms of A326835 are odd (as phi(1) = phi(2) = 1).

The corresponding numbers of divisors are 1, 2, 3, 4, 6, 8, 9, 10, 12, 16, 18, 20, 24, 32, 36, 40, 48, 64, 72, 80, 96, 128, 144, 160, 192, 256, 288, 320, 384, 512, 576, ...

Links

Table of n, a(n) for n=1..31.

Example

The sequence A326835 begins with 1, 3, 5, 7, 9, 11, 13 and 15. The number of divisors of these terms are 1, 2, 2, 2, 3, 2, 2 and 4, respectively. The record values, 1, 2, 3 and 4, occur at 1, 3, 9 and 15, the first 4 terms of this sequence.

Mathematica

q[n_] := Length @ Union[EulerPhi /@ (d = Divisors[n])] == Length[d]; dm = 0; s = {}; Do[If[q[n], d = DivisorSigma[0, n]; If[d > dm, dm = d; AppendTo[s, n]]], {n, 1, 10^6, 2}]; s

Crossrefs

Cf. A326835, A328858, A348199.

Sequence in context: A355772 A355771 A053624 * A119239 A140864 A171929

Adjacent sequences: A348195 A348196 A348197 * A348199 A348200 A348201

Keyword

nonn,more

Author

Amiram Eldar, Oct 06 2021

Status

approved