Here is last week's puzzle, as originally posted: Perfect numbers are numbers that equal the sum of their divisors. For example, the number 6 can be divided evenly by 1, 2, and 3, and 6 = 1 + 2 + 3.

The Monthly publishes articles, as well as notes and other features, about mathematics and the profession. Its readers span a broad spectrum of mathematical interests, and include professional ...

A recursive scheme for determination of the sum-of-divisors function is presented. As all of the formulas involve triangular numbers, the scheme is therefore compared for efficiency with another known ...