3. As shown in the figure, a toy ant starts crawling from point $O$. On the $n$-th time, it first crawls $n$ units to the right, then $n$ units upwards, reaching point $A_{n}$. Then, it continues crawling from point $A_{n}$. If point $O$ is denoted as $(0,0)$, point $A_{1}$ as $(1,1)$, point $A_{2}$ as $(3,3)$, point $A_{3}$ as $(6,6), \cdots$, then point $A_{100}$ is denoted as $\qquad$.
3. As shown in the figure, a toy ant starts crawling from point $O$. On the $n$-th time, it first crawls $n$ units to the right, then $n$ units upwards, reaching point $A_{n}$. It then continues to crawl from point $A_{n}$. If point $O$ is denoted as $(0,0)$, point $A_{1}$ as $(1,1)$, point $A_{2}$ as $(3,3)$, point $A_{3}$ as $(6,6), \cdots$, then point $A_{100}$ is denoted as $\qquad$【Solution】Solution: According to the analysis, $A_{100}$ is denoted as $(1+2+3+\cdots+100,1+2+3+\cdots+100)$;

Since $1+2+3+\cdots+100=(1+100) \times 100 \div 2=5050$,
Therefore, $A_{100}$ is denoted as $(5050,5050)$;
Hence, the answer is: $A_{100}$ is denoted as $(5050,5050)$.