I don't recognize that beep code, but it is also possible that you are getting some beeps from USB devices. See Server Products — Not all beep codes signal an error
Does the server stop booting after the beeps, with no display? If so, the best thing to test is, temporarily remove the memory and all USB devices, then boot up, and make sure you get only three beeps.
If that works, check your memory against the Server Products — Tested memory and hardware list