1019999domain: NAppears in sequencesNumbers n such that n' = p^2-1, with n = semiprime = p*q, n' is the arithmetic derivative of n. Also: semiprimes of the form p*(p^2-p-1).at n=12A190274Number of arrays of median of three adjacent elements of some length 6 0..n array, with no adjacent equal elements in the latter.at n=33A229014