The steps to solve the puzzle are:
1) Approach the triangle and press the A Button
2) Press Left 5 times then press Down one time, now press A
3) Press Right 5 times, then press Up 5 times, then press A
4) Press Right 5 times, Press Down 5 times, and press A
5) Press Up 3 times, Left 7 times, press the A button
6) Press Right 5 times, then press the A button
7) Press Left 3 times, Down 2 times, and press A
8) Press Down once, then press left 4 times, then press A
9) Press Right 7 times, then press A
10)Press Left 4 times, Down one time and press A
11)Press up 4 times, then press A
12)Save your game now, the next time you touch the triangle Deoxys will apear.
13)Now press A and Deoxys will apear, lower its health and put it to sleep if possible. Then start throwing Timer Balls and Ultra Balls untill you catch it.