1539720

Appears in sequences

• Harmonic or Ore numbers: numbers k such that the harmonic mean of the divisors of k is an integer.at n=33A001599
• Numbers whose divisors' harmonic and arithmetic means are both integers.at n=29A007340
• Expansion of 1/((1-2*x)*(1-5*x)*(1-9*x)*(1-12*x)).at n=5A026108
• Numbers n such that harmonic mean of the divisors of n is a prime.at n=12A074247
• Harmonic numbers (A001599) which are not perfect (A000396).at n=29A090945
• Harmonic numbers that are not multiply-perfect.at n=25A140798
• Numbers n such that sigma(n+sigma(n)) = 5*sigma(n).at n=30A246912
• 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=23A325022
• Harmonic numbers k such that k*p is not a harmonic number for all the primes p that do not divide k.at n=15A335369