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A065819 revision #13

A065819

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

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

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Table of n, a(n) for n=1..35.

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

EXAMPLE

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

MATHEMATICA

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

PROG

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

CROSSREFS

Cf. A000010, A000203, A062699.

Sequence in context: A157775 A300619 A275822 * A241649 A256288 A302107

Adjacent sequences: A065816 A065817 A065818 * A065820 A065821 A065822

KEYWORD

nonn

AUTHOR

Labos Elemer, Nov 23 2001

STATUS

editing