# Greetings from The On-Line Encyclopedia of Integer Sequences! http://oeis.org/ Search: id:a075868 Showing 1-1 of 1 %I A075868 #2 Feb 11 2014 19:05:31 %S A075868 3,6,15,20,21,28,35,50,66,98,99,104,105,114,125,130,154,170,210,230, %T A075868 276,325,351,352,363,372,374,380,414,444,459,476,532,539,558,572,580, %U A075868 585,608,666,693,696,845,847,950,968,975 %N A075868 tau(n) = phi(sum of prime factors of n). %e A075868 tau(50) = number of divisors of 50 = 6; phi(sum of prime factors of 50) = phi(2 + 5) = 6. Hence 50 is a term of the sequence. %t A075868 Select[Range[2, 10^3], EulerPhi[Apply[Plus, Transpose[FactorInteger[ # ]][[1]]]] == DivisorSigma[0, # ] &] %K A075868 nonn %O A075868 2,1 %A A075868 _Joseph L. Pe_, Oct 15 2002 # Content is available under The OEIS End-User License Agreement: http://oeis.org/LICENSE