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5
2016 Algebra #5
2016 Algebra #5
Source:
December 24, 2016
Problem Statement
An infinite sequence of real numbers
a
1
,
a
2
,
…
a_1, a_2, \dots
a
1
,
a
2
,
…
satisfies the recurrence
a
n
+
3
=
a
n
+
2
−
2
a
n
+
1
+
a
n
a_{n+3} = a_{n+2} - 2a_{n+1} + a_n
a
n
+
3
=
a
n
+
2
−
2
a
n
+
1
+
a
n
for every positive integer
n
n
n
. Given that
a
1
=
a
3
=
1
a_1 = a_3 = 1
a
1
=
a
3
=
1
and
a
98
=
a
99
a_{98} = a_{99}
a
98
=
a
99
, compute
a
1
+
a
2
+
⋯
+
a
100
a_1 + a_2 + \dots + a_{100}
a
1
+
a
2
+
⋯
+
a
100
.
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