I am interested in translating the word "then" in logical statements like this: "If a number is prime, then it is squarefree." Or maybe better: "If x is even and x+y is odd, then y is odd." In common language one would not use a "then" at all, but in mathematics (including logic) it is very common to emphasize the consequence with a "then". This logical "then" is not temporal but causal, and I have never seen it in ancient sources at all. I have not found this sense of "then" in Latin dictionaries.
What would be a good translation of this "then"? Was there a fixed phrase in the mathematical Latin of, say, 18th and 19th century? My intuition is to translate "if–then" with si–deinde. I want something that works within a sentence, so that the "then" does not start a stand-alone sentence, but just a consequence clause.
It seems that Gauss does not use a "then" at all in this example. It is possible that the logical "then" was introduced after Latin went out of fashion in mathematics.