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%I #9 Feb 11 2014 19:05:30
%S 15,35,357,1045,3339,5049,10659,12441,24871,24969,29029,50065,58435,
%T 64285,87685,99693,132957,137885,140335,353133,423657,596037,655707,
%U 734517,745503,894387,1390753,1406427,1529983,1641783,1739507,1823877
%N Numbers n such that sigma(n) = phi(3n).
%H Donovan Johnson, <a href="/A074891/b074891.txt">Table of n, a(n) for n = 1..500</a>
%e sigma(15) = 24 = phi(3 * 15), so 15 is a term of the sequence.
%t Select[ Range[1936556], EulerPhi[3# ] == DivisorSigma[1, # ] &]
%o (PARI) is(n)=sigma(n)==eulerphi(3*n) \\ _Charles R Greathouse IV_, Dec 09 2013
%K nonn
%O 1,1
%A _Joseph L. Pe_, Sep 13 2002
%E Edited and extended by _Robert G. Wilson v_, Sep 17 2002
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