389593

Appears in sequences

• Hyperperfect numbers: k = m*(sigma(k) - k - 1) + 1 for some m > 1.at n=25A007592
• Hyperperfect numbers: x such that x = 1 + k*(sigma(x)-x-1) for some k > 0.at n=29A034897
• Semiprimes pq with pq - 1 divisible by p + q.at n=16A164643
• Triangle, read by rows, T(n, k) = Sum_{j=0..k} (n+k)!/((n-j)!*(k-j)!*j!) + Sum_{j=0..n-k} (2*n-k)!/((n-j)!*(n-k-j)!*j!).at n=15A176081
• Triangle, read by rows, T(n, k) = Sum_{j=0..k} (n+k)!/((n-j)!*(k-j)!*j!) + Sum_{j=0..n-k} (2*n-k)!/((n-j)!*(n-k-j)!*j!).at n=20A176081
• Unitary hyperperfect numbers.at n=30A225150
• Bi-unitary k-hyperperfect numbers: numbers m such that m = 1 + k * (bsigma(m) - m - 1) where bsigma(m) is the sum of bi-unitary divisors of m (A188999) and k >= 1 is an integer.at n=23A309568