Is "Allahumma innaka 'afuwwun tuhibbul 'afwa, fa'fu 'anni" a formula for seeking forgiveness, and is it sufficient to recite it a specific number of times?

The supplication for pardon is not the same as the request for forgiveness, neither linguistically nor Islamically. Forgiveness, according to many scholars, is more profound than pardon. Sheikh Al-Islam Ibn Taymiyyah said: "Pardon implies the dropping of one's right against them and overlooking it. Forgiveness, however, implies protecting them from the evil of their sins, His turning towards them, and His satisfaction with them; unlike mere pardon. For the pardoner may pardon, yet not turn towards the one he pardoned, nor be pleased with him. Thus, pardon is a mere omission, while forgiveness is beneficence, grace, and generosity." A Muslim should combine these supplications and frequently seek forgiveness and ask for pardon. There is no harm in repeating the request for pardon any number of times, as long as one does not believe that a specific number has a particular virtue.