Let $${x_n}$$ denote the number of binary strings of length $$n$$ that contains no consecutive $$0s$$.

Which of the following recurrences does $${x_n}$$ satisfy?

The exponent of $$11$$ in the prime factorization of $$300!$$ is

In how many ways can $$b$$ blue balls and $$r$$ red balls be distributed in $$n$$ distinct boxes?

When $$n = {2^{2k}}$$ for some $$k \ge 0$$, the recurrence relation $$$T\left( n \right) = \sqrt 2 T\left( {n/2} \right) + \sqrt n ,\,\,T\left( 1 \right) = 1$$$
evaluates to