Excel formula that identifies the next number in the series.

Hello ladies and gents,

I have a rather simple question but I cant get my head round to it. I'm hoping you can help.

Here is my question.

Say i have a series of number like below in Cell A1 to A5. In Cell B1, I want excel to tell me what should be next number in the series.. Is there a way of doing this using just formula or it can only be done using VBA?

Column A
1
2
3
4
5

Thank you very much in advance.

Best Regards,