You know of this? https://en.wikipedia.org/wiki/Wow!_signal
SETI at Home was a screensaver that was looking for signals like that via distributed searching and they didn't find anything (but they do have telescope time for tackling the 92 highest priority follow-up scans).
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https://news.ycombinator.com/item?id=45077654
https://news.ycombinator.com/item?id=43979537
https://news.ycombinator.com/item?id=43085967
https://news.ycombinator.com/item?id=35210503