121679

Appears in sequences

• Numbers n such that sigma(phi(n))/sigma(n) is an integer >= 4.at n=0A066881
• Numbers n such that sigma(phi(n))/sigma(n) = 4.at n=0A067384
• a(n) is smallest x such that sigma(phi(x))/sigma(x) = n.at n=3A067385
• a(n) = 80*n^2 - 1.at n=38A158774
• a(n) = 5*a(n-1) - 10*a(n-2) + 8*a(n-3) with a(0) = 2, a(1) = a(2) = 3.at n=16A247565