Replying to a query by Bob Solovay, Ron Graham wrote: > This real is well known to be e^(1/e) Just to comment that this number has a nostalgic interest for me. When I was a freshman I managed to prove that the sequence defined by s_1=x, s_{n+1} = x^(s_n) converges precisely for real numbers x satisfying (1/e)^e <= x <= e^{1/e). Martin