e (MATH)
The mathematical constant e (occasionally called Euler's number after the Swiss mathematician Leonhard Euler, or Napier's constant in honor of the Scottish mathematician John Napier who introduced logarithms) is the base of the natural logarithm function. Its value is 2.71828 18284 59045 23536 02874 7135...
It's most common definition is the infinite sum of progressing factorialized (!) fractions (x/y), or 1/0! + 1/1! + 1/2! + 1/3! + 1/4! + 1/5! + ... + 1/∞!. Please note that these fractions are expressed as x/(y!) not (x/y)!.
Alongside the number p and the imaginary unit i, e is one of the most important mathematical constants. It has a number of equivalent definitions; some of them are given below. e, just like π is an irrational number and has an infinite number of digits. Although not as internationally acclaimed as π it still has many beirings in the mathimatical world.
e IN THE NON-MATHIMATICAL WORLD
In the IPO filing for Google Inc., in 2004, rather than a typical round-number amount of money, the company announced its intention to raise $2,718,281,828, which is, of course, e billion dollars rounded to the nearest dollar.
Google was also the culprit of a mysterious billboard that appeared in the heart of Silicon Valley, and later in Cambridge, Massachusetts, which read {first 10-digit prime found in consecutive digits of e}.com. Once solving this problem (the first 10-digit prime in e is 7427466391, which surprisingly starts as late as the 101st digit), and visiting the web site advertised, there was an even more difficult problem to solve that also had to do with digits in e. Google seems to have an attraction to e, for some unknown reason.
Donald Knuth, the famous computer scientist let the version-numbers of his book METAFONT approach e (i.e the versions are 2, 2.7, 2.71, 2.718, etc.)
See Also: The First Stop on the e Tour
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