The Numbers discovered in an old French comic strip

Thanks to Nico from LOSTpedia-FR for the following.

On our forum, someone just found something really amazing in the very popular Spirou et Fantasio French comic strips! In Spirou à Moscou, the 42nd album of the series, released in 1990, a character (Zantafio) returns and Spirou recalls to Fantasio that Zantafio has done the most horrible things. After that, there is an asterisk which leads to the bottom of the page where you can read: "Do you want to know them, dear reader? They are denounced in albums #4, 7, 8, 16, 23 and 42." And those albums were relased from 1952 to 1990! Can it be a coincidence??