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Cono Sur Olympiad
2023 Cono Sur Olympiad
4
4
Part of
2023 Cono Sur Olympiad
Problems
(1)
Easy NT sequence
Source: Cono Sur 2023 P4
8/8/2023
Consider a sequence
{
a
n
}
\{a_n\}
{
a
n
}
of integers, satisfying
a
1
=
1
,
a
2
=
2
a_1=1, a_2=2
a
1
=
1
,
a
2
=
2
and
a
n
+
1
a_{n+1}
a
n
+
1
is the largest prime divisor of
a
1
+
a
2
+
…
+
a
n
a_1+a_2+\ldots+a_n
a
1
+
a
2
+
…
+
a
n
. Find
a
100
a_{100}
a
100
.
number theory