804384

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=4A066784
• Partition number array, called M32(-4), related to A011801(n,m)= |S2(-4;n,m)| ( generalized Stirling triangle).at n=31A144267
• Numbers k for which sigma(k)/k - 4/7 is an integer.at n=3A218411
• Numbers k such that k = Sum_{i=1..j} (d_i mod d), where d_i are their aliquot parts and d is one of them.at n=37A265646
• 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=31A286876
• 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=4A349746
• Numbers k for which k * gcd(sigma(k), A276086(k)) is equal to sigma(k) * gcd(k, A276086(k)), where A276086 is the primorial base exp-function, and sigma gives the sum of divisors of its argument.at n=12A351458