237961domain: NAppears in sequencesNumbers n such that sigma(phi(n))/sigma(n) = 3.at n=30A067383Six-digit integers that are concatenation and product of three 2-digit primes.at n=14A180467Triangle read by rows, T(n,k) = Sum_{j=0..n-k+1} j!*C(n-1,j-1)*T(n-j,k-1) if k != 0 else 1, n>=0, 0<=k<=n.at n=50A256895