GAP 4.8.9 installation with standard packages -- copy to your CoCalc project to get it
\BOOKMARK [0][-]{chapter.1}{The 3k+1 Problem}{}% 1
\BOOKMARK [1][-]{section.1.1}{Theory}{chapter.1}% 2
\BOOKMARK [1][-]{section.1.2}{Program}{chapter.1}% 3
\BOOKMARK [0][-]{chapter*.3}{References}{}% 4
\BOOKMARK [0][-]{section*.4}{Index}{}% 5