[1]
Brookshear, J. G. Theory of Computation: Formal Languages, Automata, and Complexity. Benjamin/Cummings, Redwood City, CA, 1989. Shows the relationships of the theoretical aspects of computer science to set theory and the integers.
[2]
Hardy, G. H. and Wright, E. M. An Introduction to the Theory of Numbers. 6th ed. Oxford University Press, New York, 2008.
[3]
Niven, I. and Zuckerman, H. S. An Introduction to the Theory of Numbers. 5th ed. Wiley, New York, 1991.
[4]
Vanden Eynden, C. Elementary Number Theory. 2nd ed. Waveland Press, Long Grove IL, 2001.