
abc-hits
Problem 127
Published on Friday, 1st September 2006, 06:00 pm; Solved by 2788The radical of n, rad(n), is the product of distinct prime factors of n. For example, 504 = 23
32
7, so rad(504) = 2
3
7 = 42.
We shall define the triplet of positive integers (a, b, c) to be an abc-hit if:
- GCD(a, b) = GCD(a, c) = GCD(b, c) = 1
- a
b - a + b = c
- rad(abc)
c
For example, (5, 27, 32) is an abc-hit, because:
- GCD(5, 27) = GCD(5, 32) = GCD(27, 32) = 1
- 5
27 - 5 + 27 = 32
- rad(4320) = 30
32
It turns out that abc-hits are quite rare and there are only thirty-one abc-hits for c
1000, with
c = 12523.
Find
c for c
120000.