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National and Regional Contests
PEN Problems
PEN P Problems
14
14
Part of
PEN P Problems
Problems
(1)
P 14
Source:
5/25/2007
Let
n
n
n
be a non-negative integer. Find all non-negative integers
a
a
a
,
b
b
b
,
c
c
c
,
d
d
d
such that
a
2
+
b
2
+
c
2
+
d
2
=
7
ā
4
n
.
a^{2}+b^{2}+c^{2}+d^{2}= 7 \cdot 4^{n}.
a
2
+
b
2
+
c
2
+
d
2
=
7
ā
4
n
.
Additive Number Theory