1. The problem is to find the sum of the integers from 1 to 13. 2. The formula to find the sum of the first $n$ natural numbers is: $$ S = \frac{n(n+1)}{2} $$ where $S$ is the sum and $n$ is the last number in the sequence. 3. Here, $n = 13$. Substitute this value into the formula: $$ S = \frac{13(13+1)}{2} $$ 4. Simplify inside the parentheses: $$ 13 + 1 = 14 $$ 5. Multiply the numbers in the numerator: $$ 13 \times 14 = 182 $$ 6. Divide by 2 to get the sum: $$ S = \frac{182}{2} = 91 $$ 7. Therefore, the sum of the integers from 1 to 13 is 91.