A riddle

You are a scientist trying to figure out a certain rule. The rule concerns sequences of three numbers - some sequences satisfy it, others don't.

You have an experimental setup you can use: you can enter a sequence of three integers, separated with commas, and it will tell you whether the sequence satisfies the rule.

You can perform the experiment arbitrarily many times. Once you think you know what the rule is, you can click "Show the solution" below in order to check if you are right.

You also get a hint to get you started: the sequence 2, 4, 6 satisfies the rule.

Good luck!