Workaround for backreference

[Kibukx]

I'm currently trying to get strings that contain 3 or more consecutive characters with the following regex:

SELECT *
FROM test.test
WHERE REGEXP_CONTAINS(first_name, r'(.)\1{2,}')

for example: "mikeeee", "dylaaan", etc but bigquery complains

Cannot parse regular expression: invalid escape sequence: \1

how can I get around this limitation since I'm aware that backreference isn't supported. Any help would be much appreciated!