Dipanjan pointed out a mistake in the explanation of exponentiation. The test says:
Quote:
For the previous example, the binary representation of 6 is 110 so the second and third powers of 2 are included: 2^2 and 2^4.

This should say:
Quote:
For the previous example, the binary representation of 6 is 110 so the second and third powers of 2 are included: 2^1 = 2 and 2^2 = 4.

(Here I've used ^ to mean exponentiation because the forum doesn't seem to be able to display exponents easily.)
Thanks again Dipanjan!