What's the difference between the LM2917 and the LM2917-N?
N is TI's designation for their Plastic DIP through hole package. Note that the SMD SOIC package designation is M.

Note, these are old ICs first designed by National Semi in the 1970s (This App note is from 1976) and later cloned by everybody. TI eventually acquired NatSemi in the 2000s and absorbed their ICs into their product lines.

I believe but can't find the original first revision datasheets to confirm, that these ICs first came out when Ceramic DIP were still common, so the N designator for moulded plastic DIP was important to point out the difference. -8 at the end also designated it as the 8 pin version, so LM2917N-8 is the 8 pin PDIP.