520625domain: NAppears in sequencesa(n) = n^2 * (4*n^2 - 1) / 3.at n=25A187756Numbers that are multiple-digit narcissistic numbers in exactly four bases.at n=18A256363Numbers k such that k' = concat(s,t) and k = s*t, where k' is the arithmetic derivative of k.at n=21A272780