Find the missing term The sequence $10000, 121, 100, 31, 24, n, 20$ represents a number $x$ with respect to different bases. What is the missing number, $n$?
This is from my elementary computer aptitude paper. Is there any way to solve this quickly?

The bases are 2,3,4,5,6,7,8, expressing values 1*16=16, 9 + 6 + 1 = 16, 1*16=16, 15 + 1 = 16, 12 + 4 = 16, 7*x + y = 16, and 2*8 = 16.  x and y are then 2 and 2.
