Pentatonix, the five-member American a cappella group lost their vocalist Avi Kaplan in 2017 at the same time as their tribute to which group received over 250 million views?
Pentatonix:  With over 13 million subscribers and 2.4 billion views, Pentatonix's YouTube channel is currently the 50th most-subscribed YouTube channel. Pentatonix:  The group's video tribute to Daft Punk had received over 250 million views as of mid 2017. Avi Kaplan:  He is known for his bass voice, and often acted as the vocal bass of Pentatonix. Avi Kaplan:  In May 2017, Kaplan announced that he was leaving Pentatonix following their upcoming tour.
i don't know