A027623 gives the number of rings with n elements, and looks empirically to be multiplicative. Is there some reason to believe that if gcd(x,y) = 1, a(xy) = a(x)a(y)? Maybe a finite-ring analogue to Sylow's theorem for finite abelian groups? - David W. Wilson "Truth is just truth -- You can't have opinions about the truth." - Peter Schickele, from P.D.Q. Bach's oratorio "The Seasonings"