# Thread: sequence question

1. ## sequence question

Hey everyone, I have a simple question.

How can I find a formula for the following sequences (like in the form ((n+1)n)/2 etc):

0,0,1,1,2,4,7,13,24

and

2,1,3,4,7,11,19,30

Thanks

2. Originally Posted by Nguyen
How can I find a formula for the following sequences (like in the form ((n+1)n)/2 etc)...
You can find formulae by trying different options, set-ups, and techniques. In other words, use intelligent guessing.

Originally Posted by Nguyen
0,0,1,1,2,4,7,13,24
0 + 0 + 1 = 1
0 + 1 + 1 = 2
1 + 1 + 2 = 4
1 + 2 + 4 = 7

...and so forth.

3. Originally Posted by stapel
You can find formulae by trying different options, set-ups, and techniques. In other words, use intelligent guessing.

0 + 0 + 1 = 1
0 + 1 + 1 = 2
1 + 1 + 2 = 4
1 + 2 + 4 = 7

...and so forth.
Thanks stapel, I looked at that website and keep trying my second sequence with a_(n-1), a_(n-2), a_(n+1), a_(n+2), etc and other techniques on that site but can't seem to find the pattern. That 19 is a problem for me! I want to know what number comes after 30, but I just can't get it. Anyone have any thoughts?

Thanks

4. Originally Posted by Nguyen
Thanks stapel, I looked at that website and keep trying my second sequence with a_(n-1), a_(n-2), a_(n+1), a_(n+2), etc and other techniques on that site but can't seem to find the pattern. That 19 is a problem for me! I want to know what number comes after 30, but I just can't get it. Anyone have any thoughts?
Thanks
The sequence you have: 2,1,3,4,7,11,19,30
contains an obvious typo: the 19 should be 18, meaning the 30 should be 29

5. Originally Posted by Wilmer
The sequence you have: 2,1,3,4,7,11,19,30
contains an obvious typo: the 19 should be 18, meaning the 30 should be 29
I believe it is not a typo.

6. Do you also believe that the start of 2,1,3 is correct, not 1,2,3 ?

All I can say is "have fun"....

7. Originally Posted by Wilmer
Do you also believe that the start of 2,1,3 is correct, not 1,2,3 ?

All I can say is "have fun"....
Yes, this question has been in the lecture notes for a long time to my knowledge. I believe how it it stated is correct. I can't do it so that is why I am asking for some expert help. It might be a trick question or something. If others think that the sequence 2,1,3,4,7,11,19,30 has a typo in it and therefore finding the next term can't be done then o.k.

8. Reason I mentionned the start of 2,1,3 may be really 1,2,3 is this sequence
which seems to be the one you're after:
3,4,7,11,19,30 - OEIS Search Results

If you ask me, it's kind of something "silly".

9. Originally Posted by Wilmer
Reason I mentionned the start of 2,1,3 may be really 1,2,3 is this sequence
which seems to be the one you're after:
3,4,7,11,19,30 - OEIS Search Results

If you ask me, it's kind of something "silly".
I think these questions in general are rather silly since there are infinitely many formulae we could provide for any finite sequence.

http://www.mathhelpforum.com/math-he...es-155069.html

That said, sometimes pattern searching can be fun, and it's good to be able to recognize common sequences like 0, 1, 4, 9, 25, 36, ..