Topology of Numbers
by Allen Hatcher
Publisher: Cornell University 2014
Number of pages: 122
An introductory textbook on elementary number theory from a geometric point of view, as opposed to the usual strictly algebraic approach. A fair amount of the book is devoted to studying Conway's topographs associated to quadratic forms in two variables.
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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.
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 W W L Chen - Macquarie University
An introduction to the elementary techniques of number theory: division and factorization, arithmetic functions, congruences, quadratic residues, sums of integer squares, elementary prime number theory, Gauss sums and quadratic reciprocity.
by Wissam Raji - The Saylor Foundation
These are 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 broaden the understanding of the concepts.