Welcome to this issue of Parabola incorporating Function. The issue starts with David Angell's article on solving a class of second order recurrences. Recurrence relations can look disarmingly simple because it is often a simple exercise to substitute in successive values to reveal the solution, a sequence comprised of these values. In solving recurrence relations you are seeking an algebraic expression that can be used to evaluate terms in the sequence directly, rather than recursively. In many cases it is not possible to find such an algebraic expression. Here is a rather famous example: