Ibn Abbas (may Allah be pleased with them both) says that the Prophet (peace and blessings be upon him) used to pray twenty rak'ahs and witr in Ramadan, outside of congregation.
Only Abu Shaybah Ibrahim bin Uthman al-Absi al-Kufi narrated it, and he is da'if (weak).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4615