Note that if in Google calendar you mark one of those events as spam, all the recurring ones are automatically removed, whereas if you just delete one it does not remove the others. There's a 'report spam' option (desktop only) in the little drop down options when you open the event.
I was so frustrated that reporting spam was desktop only. To add insult to injury if you try to go to the web app on your Android phone in a desktop tab it still opens the Android app instead. Since I was at work (and I don't login to any personal accounts on my work laptop) I had to use Firefox mobile to mark them all as spam.
