#JavaScript, 48 47 46 bytes

Input and output as strings. Returns the nth term of the sequence.

f=s=>s-(s=s.replace(/(.)\1/g,x=>x/5.5))?f(s):s

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• 1 byte saved thanks to Arnauld
• 1 byte saved thanks to tsh

JavaScript, 48 47 46 bytes

Input and output as strings. Returns the nth term of the sequence.

f=s=>s-(s=s.replace(/(.)\1/g,x=>x/5.5))?f(s):s

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• 1 byte saved thanks to Arnauld
• 1 byte saved thanks to tsh

#JavaScript, 48 47 bytes

Input and output as strings. Returns the nth term of the sequence.

f=s=>s-(s=s.replace(/(.)\1/g,x=>x[0]*2))?f(s):s

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1 byte saved thanks to Arnauld

#JavaScript, 48 47 46 bytes

Input and output as strings. Returns the nth term of the sequence.

f=s=>s-(s=s.replace(/(.)\1/g,x=>x/5.5))?f(s):s

Try it online

• 1 byte saved thanks to Arnauld
• 1 byte saved thanks to tsh

#JavaScript, 48 47 bytes

Input and output as strings. Returns the nth term of the sequence.

f=s=>s-(s=s.replace(/(.)\1/g,x=>x[0]*2))?f(s):s

Try it online

1 byte saved thanks to Arnauld

#JavaScript, 48 47 bytes

Input and output as strings. Returns the nth term of the sequence.

f=s=>s-(s=s.replace(/(.)\1/g,x=>x[0]*2))?f(s):s

Try it online

1 byte saved thanks to Arnauld