Dnk,
You are spot on. In a two leg _single_ phase system, you need two equal currents on each leg to balance to zero on the neutral. In a three leg _three_ phase system, you need _three_ equal currents on each leg to balance to zero on the neutral (I am assuming similar power factor and no harmonics).
If you had 10A on phase A, 10A on phase B, and 0A on phase C, then you would see _10A_ on the neutral.
Oh, for future reference, '^' is often use to mean 'raised to the power', so squared would be '^2' and cubed would be '^3'.
-Jon
