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National and Regional Contests
PEN Problems
PEN E Problems
30
E 30
E 30
Source:
May 25, 2007
Problem Statement
Given an odd integer
n
>
3
n>3
n
>
3
, let
k
k
k
and
t
t
t
be the smallest positive integers such that both
k
n
+
1
kn+1
kn
+
1
and
t
n
tn
t
n
are squares. Prove that
n
n
n
is prime if and only if both
k
k
k
and
t
t
t
are greater than
n
4
\frac{n}{4}
4
n
ā
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