fibonacci formula

A B

1 0.5
2 0.5
3 1 (0.5+0.5)
4 1.5 (0.5+1)
5 2.5 (1+1.5)
6 4 (1.5+2.5)
1 0.5
2 0.5
1 0.5
1 0.5
1 0.5
2 0.5
3 1
4 1.5
.....


I would like to make a formula for column B as in the example above

Thank you.
thank you

Hi and welcome
starting in B3 try = A1+A2 and pull down

(BTW you'll find lots of info on Fibonacci on the Net)

In your example, what happens after A6??

here is a macro I developed for kicks a few years back.

I would like to make a formula that takes into account what is in column A, if in column A appears 1, in column B start again with 0.5

Have you tried the proposed solutions?
Have you read my question?

Assuming that you have to use row 1 (or 2) as the start of your data, try the following in B3:

=IFERROR(IF(OR(A3=1,A3=2),0.5,B1+B2),0.5)
Then...
Copy this down starting in B4 as required, and also up to B1 and B2.
If you can adopt the cleaner approach by starting on row 3 or below, the IFERROR function (in bold red) will not be required.

Thank You Hercules1946, it works.

I would have another question.
I have a column C with n positions and values, I would like in column B to display the corresponding value in column C, ie if in column A the string is reset after position 6, column B will show the 6th value in the column C, if in column A the string resets to position 2, column B will show the second value in column C.

A B -----C


1 0------7
2 0------9
3 0 -----13
4 0 -----25
5 0 -----50
6 70 ----70
1 0 ------80
2 9 ------100
1 7 ------120
1 7 ------180
1 0 ------250
2 0 ------270
3 0
4 25


Is it possible to do this in excel?