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

Author

Amiram Eldar, May 30 2020

Keywords

• nonn
• more

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.

Examples

			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.
		

Crossrefs

Cf. A000010, A000203, A018894, A020492.

Programs

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