1284192

Appears in sequences

• Numbers n such that (n, sigma(n)) lies on the hyperbola y^2 - x^2 = m^2, for some natural number m, i.e., sigma(n)^2 - n^2 = m^2.at n=6A066784
• Numbers k for which sigma(k)/k - 4/7 is an integer.at n=6A218411
• Numbers n such that the set of prime divisors of n is equal to the set of prime divisors of sum of proper divisors of n while n is not in A027598.at n=34A286876
• Composite k for which lcm(k, phi(k)) + lcm(k, tau(k)) = lcm(k, sigma(k)).at n=17A328651
• Numbers m such that there are at least two smaller numbers k < m with the same harmonic mean of divisors as m.at n=2A348697