Is the prostration of forgetfulness (sujud al-sahw) obligatory for the imam who forgot to say the takbir (Allahu Akbar) when rising from the prostration of recitation (sujud al-tilawah) in an obligatory prayer, and should it be before or after the salam?

The takbir (saying "Allahu Akbar") when prostrating for recitation (sujud al-tilawah) and when rising from it during prayer is legislated, due to the general practice of the Prophet, peace be upon him, of saying takbir with every lowering and rising. If a worshipper forgets the takbir for sujud al-tilawah, he does not perform sujud al-sahw (prostration of forgetfulness) according to the majority of scholars. However, the Hanbalis hold that saying takbir for it is obligatory, and takbir must be said both when prostrating and when rising.