459818240

Appears in sequences

• 3-perfect (triply perfect, tri-perfect, triperfect or sous-double) numbers: numbers such that the sum of the divisors of n is 3n.at n=3A005820
• Multiply-perfect numbers: n divides sigma(n).at n=15A007691
• Let sigma_m (n) be result of applying sum-of-divisors function m times to n; call n (m,k)-perfect if sigma_m (n) = k*n; sequence gives the (2,12)-perfect numbers.at n=5A019289
• Erroneous version of A005820.at n=3A039688
• Multiply perfect numbers that are also harmonic numbers but are not arithmetic numbers.at n=6A046986
• Numbers k whose average divisor is nonintegral and divides k.at n=8A046999
• Numbers n such that sigma(n) / n is prime.at n=8A065997
• Abundant numbers n such that n = sigma(k) - 2k, where k = sigma(n) - 2n.at n=5A069085
• Numbers k such that sigma(k)/k, sigma_3(k)/k and sigma_5(k)/k are all integers.at n=8A076231
• Numbers k such that sigma(k)/k and sigma_3(k)/k are both integers.at n=11A076233
• Numbers k such that sigma(k)/k, sigma_3(k)/k, sigma_5(k)/k and sigma_7(k)/k are all integers.at n=7A076234
• Numbers k that divide (sum of proper divisors of k + product of proper divisors of k).at n=15A089748
• OU-Sigma multiperfect numbers.at n=20A091321
• Admirable numbers that set a new record for largest subtracted divisor.at n=15A109745
• Let S(n)=sigma(|n|)-2*n; sequence gives numbers n such that S(S(S(S(n))))=n. May be called {2,1}-Sociable number of orders 1 or 2 or 4.at n=22A113285
• Let S(n)=sigma(n)/3. Numbers k such that S(S(k))=k, 1/3-sociable number of order 1 or 2.at n=9A113546
• Multiply perfect numbers k such that sigma(k)/k > 2.at n=9A166069
• Numbers n such that gcd(sigma(n), n) > gcd(sigma(m), m) for all m < n.at n=28A216793
• Numbers k such that k divides sigma(3*k).at n=35A227303
• Numbers k that divide 2*sigma(k).at n=25A246454