55205domain: NAppears in sequencesa(n) = n * (2*n - 1)!! - Sum_{k=0..n-1} a(k) * (2*n - 2*k - 1)!!.at n=5A004208RMS values of the RMS numbers: a(n) is the root mean square of the divisors of A140480(n).at n=19A141812RMS values of the Primitive RMS numbers: a(n) is the Root Mean Square of the divisors of A141813(n).at n=10A141814