Bracket number
From timescalewiki
Let $\mathbb{T}$ be a time scale and define the bracket numbers (they are actually functions) by $$[n]_{\mathbb{T}} = \left\{ \begin{array}{ll} 0 &; n=0 \\ [n-1]_{\mathbb{T}} \boxplus_{\mu} 1 &; n=1,2,\ldots \end{array} \right.,$$ where $\boxplus$ denotes the forward box plus operation.
