5. Recursion and Iteration
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10, 41, 165, 661, 2645
a_1&=10 a_(n+1)&=4a_n+1 To do so, we will use a table. To find a_2, we will substitute 1 for n in the above formula. To find a_3, we will substitute 2 for n, and so on.
| n | a_(n+1)=4a_n+1 | 4a_n+1 | a_(n+1) |
|---|---|---|---|
| - | a_1= 10 | - | - |
| 1 | a_(1+1)=4a_1+1 ⇕ a_2=4a_1+1 |
a_2=4 a_1+1 ⇓ a_2=4( 10)+1 |
a_2= 41 |
| 2 | a_(2+1)=4a_2+1 ⇕ a_3=4a_2+1 |
a_3=4 a_2+1 ⇓ a_3=4( 41)+1 |
a_3= 165 |
| 3 | a_(3+1)=4a_3+1 ⇕ a_4=4a_3+1 |
a_4=4 a_3+1 ⇓ a_4=4( 165)+1 |
a_4= 661 |
| 4 | a_(4+1)=4a_4+1 ⇕ a_5=4a_4+1 |
a_5=4 a_4+1 ⇓ a_5=4( 661)+1 |
a_5= 2645 |
The first five terms of the sequence are 10, 41, 165, 661, and 2645.