Number of ways of partitioning a string of alphabetical characters with two two letters?

Given a string constituting of only two characters, like 'FFA' ,'OOPP' or ' GGGD' , in how many ways could one partition it into groups of letters?.ie for GGGD we have 7 ways of doing this namely: GGGD or G,GGD or G,G,GD or G,G,G,D or G,GG,D or GGG,D or GG,GD . How would we compute this for larger strings such as 'PPPPPPGGGGG' or 'DDDDDDDDDDDDDDEEEEEEEE'?(Sorry about the typo with the title, I meant 'two letters' not 'two two letters')

Easy Math Editor

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`2 \times 3`	$2 \times 3$
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Math	Appears as
Remember to wrap math in `\(` ... `\)` or `\[` ... `\]` to ensure proper formatting.
`2 \times 3`	$2 \times 3$
`2^{34}`	$2^{34}$
`a_{i-1}`	$a_{i-1}$
`\frac{2}{3}`	$\frac{2}{3}$
`\sqrt{2}`	$\sqrt{2}$
`\sum_{i=1}^3`	$\sum_{i=1}^3$
`\sin \theta`	$\sin \theta$
`\boxed{123}`	$\boxed{123}$