A165630 Numbers n such that sigma(n)/phi(n) = 25/9, where sigma = A000203, phi = A000010.

8721, 10179, 21489, 99813, 203721, 228417, 229653, 250705, 268047, 609957, 1150713, 1343277, 2429283, 2835417, 2835807, 2881197, 3150333, 3230469, 3833181, 4679157, 4885569, 5673291, 6082527, 6302529, 6713637, 6819879, 7096329, 9464121, 10313979, 12168651

Offset

1,1

Comments

A subsequence of A011257. Contains the product m*n of relatively prime (gcd(m,n)=1) terms (m,n) in A164647 x A164648.

Links

Donovan Johnson, Table of n, a(n) for n = 1..1000

Mathematica

Select[Range[122*10^5], DivisorSigma[1, #]/EulerPhi[#]==25/9&] (* Harvey P. Dale, Jun 20 2021 *)

Prog

(PARI) for( i=1, 1e7, sigma(i)/eulerphi(i)==25/9 && print1(i", "))

Crossrefs

Sequence in context: A266578 A031852 A115614 * A250999 A214171 A067867

Adjacent sequences: A165627 A165628 A165629 * A165631 A165632 A165633

Keyword

nonn

Author

Farideh Firoozbakht and M. F. Hasler, Sep 23 2009

Status

approved