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 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 R. D. Carmichael - John Wiley & Sons
The purpose of this book is to give the reader a convenient introduction to the theory of numbers. The treatment throughout is made as brief as is possible consistent with clearness and is confined entirely to fundamental matters.
by Leo Moser - The Trillia Group
The book on elementary number theory: compositions and partitions, arithmetic functions, distribution of primes, irrational numbers, congruences, Diophantine equations; combinatorial number theory, and geometry of numbers.
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.