I'm looking for a particular (actually, there are probably several) of two numbers that are "extremely close together" - by which I mean they share the first 15 or so significant digits before they differ from each other. I've seen at least one really excellent example of something like e^2pi vs. some square root or something. i.e. simple expression equals something like 29.140293501160298310107002522... and a different simple expression equals something like 29.140293501160298310107086610... (the first 24 digits are identical; then they are different.) I thought I had seen in on the Wolfram site, possibly in a discussion of extra precision, but have been searching quite unsuccessfully. Thanks.