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Recursion
easy
0:00.0
Find the 4th term of
a
n
=
2
a
n
−
1
+
1
a_n = 2a_{n-1} + 1
a
n
=
2
a
n
−
1
+
1
with
a
1
=
1
a_1 = 1
a
1
=
1
.
A
3
B
7
C
15
D
31
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