He has never revealed a definitive list of the books he did not write entirely himself. However, here's what we know:
* Stine's writing process: Stine has said he usually writes the first draft of a Goosebumps book and then sends it to his editor. The editor might make suggestions, and then Stine revises the book. It's possible that some of the revisions were done by another writer, though Stine has never confirmed this.
* Stine's health: Stine has also mentioned that he has had health problems that have made it difficult for him to write at times. It's possible that he had help from other writers during these periods.
* Stine's workload: Stine has written a prolific amount of books, and it's possible that he couldn't have written all of them himself. He has mentioned that he had help with some of the books, but he has not been specific about which ones.
Therefore, it's impossible to say for sure which Goosebumps books were ghostwritten.
If you're interested in learning more about the writing process for Goosebumps, you can read interviews with R.L. Stine or check out his website.