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Saudi Arabia Pre-TST + Training Tests
2014 Saudi Arabia Pre-TST
1.3
1.3
Part of
2014 Saudi Arabia Pre-TST
Problems
(1)
1 - 5^n + 5^{2n+1} is a perfect square
Source: 2014 Saudi Arabia Pre-TST 1.3
9/13/2020
Find all positive integers
n
n
n
for which
1
ā
5
n
+
5
2
n
+
1
1 - 5^n + 5^{2n+1}
1
ā
5
n
+
5
2
n
+
1
is a perfect square.
number theory
Perfect Square