1089270

Appears in sequences

• Harmonic or Ore numbers: numbers k such that the harmonic mean of the divisors of k is an integer.at n=31A001599
• Numbers whose divisors' harmonic and arithmetic means are both integers.at n=27A007340
• Harmonic seed numbers.at n=13A035527
• (1+e)-harmonic numbers: harmonic mean of (1+e)-divisors is an integer.at n=35A053783
• Harmonic numbers (A001599) which are not perfect (A000396).at n=27A090945
• a(n) = smallest number m such that m*tau(m)/sigma(m) = n, or 0 if no such m exists.at n=41A091911
• Numbers k such that sigma(k)*phi(k)*k is a square.at n=20A114079
• Harmonic numbers that are not multiply-perfect.at n=23A140798
• a(n) = (3^n/n!^2) * Product_{k=1..n} (6k-4)*(6k-5).at n=4A184424
• Numbers k for which sigma(k)/k - 3/7 is an integer.at n=2A218410
• Even multiply-perfect numbers divided by 2.at n=9A219544
• Numbers m such that m divides sigma(2*m).at n=14A227302
• Harmonic numbers m from A001599 such that m*(m-tau(m))/sigma(m) is not an integer, where k-tau(k) = the number of nondivisors of k (A049820), tau(k) = the number of divisors of k (A000005) and sigma(k) = the sum of the divisors of k (A000203).at n=21A325022
• Numbers k such that A007947(k) divides sigma(k) and A003557(k)-1 either divides A326143(k) [= A001065(k) - A007947(k)], or both are zero.at n=17A336550