A rectangular grid is formed using matchsticks.
A \(1 \times 1\) grid uses \(4\) matchsticks.
A \(2 \times 1\) grid uses \(7\) matchsticks.
A \(3 \times 1\) grid uses \(10\) matchsticks.
1. The general rule for \(n \times 1\) rectangular grid is .
2. The number of matchsticks needed for \(13 \times 1\) grid is .