Here's a manual method, for what it's worth. It won't fit your needs if you have serious data analysis to do (but since you are using Excel, that cannot be the case).

So you have a `12345`

column in Column A.

Create an identical `12345`

column in Column B that starts one row before (add it if necessary), and add `0`

to your initial series.

You now have the following:

```
A B
0 1
1 2
2 3
3 4
5 6
etc.
```

You now need to remove rows `01`

, `23`

, `45`

, i.e. rows that end with an odd number.

Create a new cell equal to `=ISODD(B1)`

(where `B1`

designates the first cell of the second column. Fill down.

You now have the following:

```
A B C
0 1 FALSE
1 2 TRUE
2 3 FALSE
3 4 TRUE
etc.
```

Filter the table by Column C, value `TRUE`

, and you have what you need on screen.

You can technically extend that method to any `r x c`

(row by column) application. My example is a `1 x 2`

transformation but you can iterate it as needed.