A164647 Numbers n such that sigma(n)/phi(n) = 16/9.

1463, 2945, 8255, 70091, 81809, 89999, 122759, 187625, 193039, 196469, 388585, 494665, 671365, 2311673, 2442583, 2687113, 4209985, 4705285, 4902247, 5393017, 5667389, 5866003, 9248323, 10795967, 11345411, 11670275, 11773027, 13290485, 13741273, 15978487

Offset: 1

Author

M. F. Hasler, Aug 22 2009

Keywords

• nonn

Comments

A subsequence of A011257.

Links

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

Crossrefs

Cf. A000010 (=phi), A000203 (=sigma), A068390, A163667, A164646.

Programs

PARI

for( n=1,10^7, sigma(n)==16/9*eulerphi(n) && print1(n","))

Extensions

More terms from Farideh Firoozbakht, Sep 22 2009