There are only SEVEN Orichalcum +-ses in the game. Whenever we use an Energy Crystal, Gem, Stone, or Shard, it halves the amount of items needed for synthesis. When the number of the items needed before using the Energy items is odd, when you use it, it will halve the number, true... But! It will round the number of items to a higher one. I know I'm not making sense... Look at this:
13/2 = 6.5 - But you will need 7 items (Orichalcum +-ses)
7/2=3.5 - But you will need 4 items!!!!!!
You only get 7 Orichalcum +-ses. NOT 8!!!!!!!!! Even if you do this right, it's not possible, you will need 4 for the first synthesis, and another 4 for the second. Unless, of course, Square didn't put an exception especially for Ultima Weapon...