‘ONE way’
Granted...Base this, that or the other....Nevertheless, I assume the first ‘contact’ will be a ‘signal’ and pi, i whatever base, will be universal..and a sign of understanding...
YES!
That's my point ... if we're looking for "pi", or "e", or whatever other "universal number", we need to make sure we'll recognize it when we see it. If "ET" is an octopus, he(?) probably won't use decimal numbers.
eiπ + 1 = 0 would be a great way of saying "I'm intelligent and sufficiently advanced to know math".