There were 17 generation songs when this page was created. The first is the 2nd generation’s “Kakigoori no kataomoi“, followed by the 3rd generation’s “Sanbanme no kaze“, which shows how few generation songs were released in the early days of Nogizaka46.
The 2nd gen has the fewest at 4, the 3rd gen has the most at 7, and the 4th gen has 5.
“Against” is the sole generation song for the 1st gen. All songs were performed by 1st gen members until the 2nd gen joined, but of course those songs are not counted as 1st gen songs.