AMC 10B Fall 2021 (Problem 22)
For each integer , let be the sum of all products , where and are integers and . What is the sum of the 10 least values of such that is divisible by 3?
Use 1. Sum of the first integers and 24. Square of a sum (n terms).
Using known sums:
For we need to be a multiple of . Hence .
The 10 least such values are .
(B) 197