MathDB
a \in (1,9) such (a - 1/a) is an integer (HOMC 2010 J Q4)

Source:

July 25, 2019
number theoryInteger

Problem Statement

How many real numbers a(1,9)a \in (1,9) such that the corresponding number a1aa- \frac1a is an integer?
(A): 00, (B): 11, (C): 88, (D): 99, (E) None of the above.