Halls of Ivy: 'N' is commonly used for what?
I am only giving what were exact examples I saw on the internet. Here is one:
There are a number of ways to approach finding prime factors of large
natural numbers. 13...
An old-fashioned way which is often effective is to express N as the difference of two squares, that is, to find x and y such that
N = x^2 - y^2 = (x - y)*(x + y). One way to do this is to start with
x being the integer just larger than sqrt(N),
http://mathforum.org/library/drmath/view/65801.html
mathwonk: do others believe Z stands for "zahlen"?
I thought Landau did that. I remember using his number theory book. However, it is not always the case, may have to do with the publisher. However, here are some facts:
Edmund Landau (1877-1938) denoted the set of integers by a fraktur Z with a bar over it in Grundlagen der Analysis (1930, p. 64). He does not seem to introduce symbols for the sets of rationals, reals, or complex numbers.
Q for the set of rational numbers and Z for the set of integers are apparently due to N. Bourbaki. (N. Bourbaki was a group of mostly French mathematicians which began meeting in the 1930s, aiming to write a thorough unified account of all mathematics.)
The letters stand for the German Quotient and Zahlen. These notations occur in Bourbaki's Algébre, Chapter 1. http://members.aol.com/jeff570/nth.html
So the real credit goes to a Frenchman(s), not a German?