Does anyone know if there's a way to have multiple product categories use the same product sequence using the product_sequence app?

I have product categories with subcategories, and I'd like the subcategories to use the same sequence as their parent category. Leaving the "Prefix for Product Internal Reference" field blank in the subcategory does not make it inherit the parent's sequence, and typing the same sequence name as the parent's sequence just creates a new sequence (i.e. you end up with two sequences with the same name).

Thanks,
Ken