# Problem 324: Building a tower
Let f(n) represent the number of ways one can fill a 3×3×n tower with
blocks of 2×1×1. You're allowed to rotate the blocks in any way you
like; however, rotations, reflections etc of the tower itself are
counted as distinct. For example (with q = 100000007) :f(2) = 229,f(4) =
117805,f(10) mod q = 96149360,f(103) mod q = 24806056,f(106) mod q =
30808124. Find f(1010000) mod 100000007.