We shall consider the representation of numbers as the sum of distinct unit fractions ; in particular we will answer two questions recently raised by Herbert S . Wilf . A sequence of positiveâ€¦ (More)

is called a covering system if every integer satisfies at least one of the congruences (1) . An old conjecture of P . ErdÃ¶s states that for every integer a there is a covering system with n l = c.â€¦ (More)