5099962368domain: NAppears in sequencesLet 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 (2,9)-perfect numbers.at n=7A019286Subsequence of terms of A019278 whose sum of divisors is also a term of A019278.at n=26A292949