Mathantics https://www.youtube.com/user/mathantics/featured
PBS Math club https://www.youtube.com/user/PBSMathClub/featured
Number rock math songs https://www.youtube.com/results?search_query=numberock+math+songs+
Khan Academy https://www.youtube.com/user/khanacademy
Mash Up Math https://www.youtube.com/channel/UCtBtcQJ8_jsrjPzb8i1tOsA
Teacher tube Maths https://www.youtube.com/user/teachertubemath