An Introductory Course in Elementary Number Theory
by Wissam Raji
Publisher: The Saylor Foundation 2013
Number of pages: 171
These notes serve as course notes for an undergraduate course in number theory. Proofs of basic theorems are presented in an interesting and comprehensive way that can be read and understood even by non-majors. The exercises are carefully chosen to broaden the understanding of the concepts.
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by Waclaw Sierpinski - ICM
The variety of topics covered here includes divisibility, diophantine equations, prime numbers, the basic arithmetic functions, congruences, the quadratic reciprocity law, expansion of real numbers into decimal fractions, and more.
by Joseph H. Silverman - Pearson Education, Inc.
Introductory undergraduate text designed to entice non-math majors into learning some mathematics, while at the same time teaching them how to think mathematically. The exposition is informal, with a wealth of examples that are analyzed for patterns.
by Allen Hatcher - Cornell University
An introductory textbook on elementary number theory from a geometric point of view, as opposed to the strictly algebraic approach. A fair amount of the book is devoted to studying Conway's topographs associated to quadratic forms in two variables.
by Thomas Taylor, A. J. Valpy
The substance of all that has been written on this subject by Nicomachus, Iamblichus, and Boetius, together with some particulars respecting perfect, amicable, and other numbers, which are not to be found in the writings of modern mathematicians.