396168192

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=9A066784
• Numbers k for which sigma(k)/k - 4/7 is an integer.at n=11A218411
• Numbers k for which k * gcd(sigma(k), u) is equal to sigma(k) * gcd(k, u), where u is obtained by shifting the prime factorization of k two steps toward larger primes [with u = A003961(A003961(k))].at n=10A349746