A335287 Balanced numbers (A020492) k with a record value of sigma(k)/phi(k).

1, 2, 6, 12, 30, 168, 210, 420, 840, 9240, 83160, 120120, 5165160, 26860680, 277560360, 569729160, 16522145640, 33044291280, 563462139240, 1140028049160, 1255683068640, 65361608151840, 299761858075680, 413956851628320

Offset

1,2

Comments

The corresponding record values are 1, 3, 6, 7, 9, 10, 12, 14, 15, 18, 20, 21, 22, 25, 26, 28, 30, 31, 32, 33, 35, 36, 38, 39, ...

The terms were calculated using data from Jud McCranie.

Links

Table of n, a(n) for n=1..24.

Example

The first 4 balanced numbers are k = 1, 2, 3, 6. The corresponding values of sigma(k)/phi(k) = A000203(k)/A000010(k) are 1, 3, 2, 6. The record values, 1, 3 and 6 occur at 1, 2 and 6 - the first 3 terms of this sequence.

Mathematica

s = {}; rm = 0; Do[r = DivisorSigma[1, n]/EulerPhi[n]; If[IntegerQ[r] && r > rm, rm = r; AppendTo[s, n]], {n, 1, 120120}]; s

Crossrefs

Cf. A000010, A000203, A018894, A020492.

Sequence in context: A073949 A367336 A080372 * A322804 A163087 A332654

Adjacent sequences: A335284 A335285 A335286 * A335288 A335289 A335290

Keyword

nonn,more

Author

Amiram Eldar, May 30 2020

Status

approved