55860

Appears in sequences

• Harmonic or Ore numbers: numbers k such that the harmonic mean of the divisors of k is an integer.at n=17A001599
• Numbers whose divisors' harmonic and arithmetic means are both integers.at n=14A007340
• Theta series of A_9 lattice.at n=6A008449
• Numbers k such that the set of prime divisors of k is equal to the set of prime divisors of sigma(k).at n=22A027598
• Number of reversible strings with n-1 beads of 2 colors. 4 beads are black. String is not palindromic.at n=37A032091
• (1+e)-harmonic numbers: harmonic mean of (1+e)-divisors is an integer.at n=17A053783
• The binary encoding (as a rooted planar tree) of each rooted planar binary tree. See A057123 for illustration.at n=16A057122
• Numbers k such that (k, sigma(k)) lies on a circle with integral radius centered at the origin, i.e., k^2 + sigma(k)^2 is a square.at n=31A066764
• Numbers m such that sigma(m)/m is equal to sigma(k)/k for some k being superabundant (A004394).at n=39A073349
• Duplicate of A007340.at n=14A090944
• Harmonic numbers (A001599) which are not perfect (A000396).at n=13A090945
• a(n) = smallest number m such that m*tau(m)/sigma(m) = n, or 0 if no such m exists.at n=20A091911
• Numbers k such that 2k+1, 4k+1, 6k+1 and 8k+1 are primes.at n=28A124409
• Consider the smallest k such that prime(k) > n*composite(k). Sequence gives composite(k).at n=10A125075
• Harmonic numbers that are not multiply-perfect.at n=9A140798
• Corresponding values of arithmetic means of divisors of numbers from A007340.at n=31A157848
• a(n) = the smallest natural numbers m such that product of harmonic mean of the divisors of n and harmonic mean of the divisors of m are integers.at n=40A176802
• Numbers k for which sigma(k)/k - 3/7 is an integer.at n=1A218410
• Numbers k such that the product of divisors of sigma(k) is divisible by the product of divisors of k.at n=34A219362
• Numbers such that the sum of divisors is twice the sum of the exponential divisors.at n=7A274205