Partial Sum of Consecutive Integers
Does a natural number n exist such that 1+2+3+4+…+n is a three-digit number with identical digits?
(Adapted from Mathematics Teacher (1990). March Calendar; Problem 16, p207)
Extension:
Does a natural number n exist such that 1+2+3+4+…+n is a 4-digit, 5-digit, … number with identical digits?