2021 WSMO Accuracy Round Problems/Problem 8
Problem
20 unit spheres are stacked in a triangular pyramid formation, such that the first layer has 1 sphere, the second layer has 3 spheres, the third layer has 6 spheres, and the fourth layer has 10 spheres. The radius of the smallest sphere that fully contains all of these spheres is 
where 
and 
is not divisible by the square of any prime. Find 
