Binary strings of length $n$ with $x$ zeros and longest $k$-runs of zeros

In this paper, we study $F_n(x,k)$, the number of binary strings of length $n$ containing $x$ zeros and a longest subword of $k$ zeros. A recurrence relation for $F_n(x,k)$ is derived. We expressed few known numbers like Fibonacci, triangular, number of binary strings of length $n$ without $r$-runs of ones and number of compositions of $n+1$ with largest summand $k+1$ in terms of $F_n(x,k)\mathrm{.}$ Similar results and applications were obtained for ^F${}_n(x,k),$ the number of all palindromic binary strings of length $n$ containing $x$ zeros and longest $k$-runs of zeros.