A065819 Numbers k such that 4*phi(k) = 3*sigma(k).

7, 209, 10013, 11687, 12857, 17537, 27577, 28067, 700321, 770431, 1321189, 1542281, 1681861, 1963039, 2282641, 2313961, 2664259, 3308041, 3709057, 3859207, 3929761, 4315751, 4380541, 4561381, 5193001, 5331001, 5576519, 5962333, 6561511, 7332919, 10065991, 12133627, 13678613, 14313949, 15263831

Offset: 1

Author

Labos Elemer, Nov 23 2001

Keywords

• nonn

Examples

			For m=10013, phi(m)=8640, sigma(m)=11520, 34560 = 4*phi = 3*sigma.
		

Links

• Jud McCranie, Table of n, a(n) for n = 1..10000 (first 65 terms from Harry J. Smith)

Crossrefs

Cf. A000010, A000203, A062699.

Programs

Mathematica

Do[s = 4*EulerPhi[n]-3*DivisorSigma[1, n]; If[Equal[s, 0], Print[n]], {n, 1, 10000000}]

PARI

{ n=0; for (m=1, 10^9, if (4*eulerphi(m) == 3*sigma(m), write("b065819.txt", n++, " ", m); if (n==65, return)) ) } \\ Harry J. Smith, Oct 31 2009