343976

Appears in sequences

• Numbers j such that sigma(sigma(j)) = k*j for some k.at n=42A019278
• 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 (2,7)-perfect numbers.at n=3A019284
• a(n) = Sum_{k=0..n-2} T(n,k) * T(n,k+2), with T given by A026659.at n=8A026978
• a(n) = n* - 2^(n-1), where n* (A003418) = least common multiple of the numbers [1,...,n].at n=14A059794
• a(n) = n* - 2^n, where n* (A003418) = least common multiple of the numbers [1,...,n].at n=13A067068
• Numbers n such that denominator(sigma(sigma(n))/n) = denominator(sigma(sigma(s))/s) where s = sigma(n).at n=24A275321
• Subsequence of terms of A019278 whose sum of divisors is also a term of A019278.at n=16A292949