info coreutilsto see a list of all of those commands that you keep intending to learn more about: not only seq, but also tac, paste, join, etc. There's even a "tsort" command that performs topological sort on text files(!).
What's a quick way to repeat a string in a command line? The best I can think of is something like
`perl -e 'print join ",", ("thestr")x50`
which with my best golfing is just
`perl -e '$,=",";print((thestr)x50)'`
and pretty unreadable.