https://en.wikipedia.org/wiki/List_of_The_Jackie_Gleason_Show_episodes

Now, I know that wikipedia.org is about as relibable as the Enquirer but if all of this is true (especially the part where during the episode that has the still lost episode Halloween Party For The Boss where Jackie sings: "I just love Halloween.") than that means that the person who wrote it has either A LOT of knowledge about the Gleason show and no footage or they have both the footage and the knowledge. I am thinking the former if it is true.

Now something tells me that this wiki entry is all a load of rubbish.

This isn't the first I've read about Gleason singing "I Just Love Halloween" during that broadcast. He may have sung it during the previous two Halloween shows as well.

There is no reason to doubt this list. The Paley Center has descriptions of all shows, including those more in-depth than what is available online. The Internet has allowed more access to newspapers, TV listings, etc. to also provide access to TV show descriptions, reviews, etc.