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A065818
Numbers k such that 3*phi(k) = 2*sigma(k).
4
5, 119, 3553, 4147, 8323, 198679, 218569, 248501, 298129, 468809, 547261, 1098349, 1398061, 1947379, 1990417, 3076549, 3453289, 3994753, 6969529, 7690249, 8790439, 11905457, 13097327, 14346577, 14732011, 14988967, 15286973, 16145269, 20851493, 21622867, 23083081, 24924599, 26218777, 26326867
OFFSET
1,1
LINKS
Jud McCranie, Table of n, a(n) for n = 1..10000 (first 75 terms from Harry J. Smith)
EXAMPLE
n = 3553, 3*phi(3553) = 8640 = 2*4320 = 2*sigma(3553).
MATHEMATICA
Select[Range[20000000], 3EulerPhi[#] == 2DivisorSigma[1, #] &] (* Harvey P. Dale, Apr 18 2011 *)
PROG
(PARI) { n=0; for (m=1, 10^9, if (3*eulerphi(m) == 2*sigma(m), write("b065818.txt", n++, " ", m); if (n==75, return)) ) } \\ Harry J. Smith, Oct 31 2009
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Nov 23 2001
EXTENSIONS
a(22)-a(28) from Harry J. Smith, Oct 31 2009
STATUS
approved