# Thread: [SOLVED] help with writing a recursive formula for a sequence

1. ## [SOLVED] help with writing a recursive formula for a sequence

i need to write a recursive formula for the nth term of the sequence:
2, 5, 7, 12, 19, 31,...
i can see the pattern they are increasing by but i'm horrible at figuring out how to put it into a formula... i just know how to set it up:
$a_1$=2 $a_n$=...?
any advice on how to start?

2. Hello, e____o!

i need to write a recursive formula for the nth term of the sequence:
. . 2, 5, 7, 12, 19, 31, ...

i can see the pattern they are increasing by . . . . you can?

It's a Fibonacci sequence . . .

Each term is the sum of the preceding two terms: . $a_n \:=\:a_{n-1} + a_{n-2}$

3. haha, well i thought i could see the pattern...
ok yea once i see the formula i realize how obviously easy it is XD but we never learned about a fibonacci sequence, maybe that's why? anyway thanks so much for your help!

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# what's the recursive form of 3 - 2 - 7 - 12 -17

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