346035domain: NAppears in sequencesOdd composite numbers k such that cototient(k) - phi(k) = k - 2*phi(k) is an odd prime.at n=20A083255Least k with precisely n partitions k = x + y satisfying x > 0 and k' = x' + y', where k', x', y' are the arithmetic derivatives of k, x, y.at n=16A212664