Rewrite the following sum using summation notation. Represent the index and lower limit of the summation as i and any number of your choice, respectively. Do not evaluate.

4 + 9 + 14 + 19 +...+ 59

In the sequence whose general term is provided, write the first four terms.

a_n=(-5)ⁿ

Write the equation that describes the nth term of the following arithmetic sequence: a_n = a_n-1 + 12, a₁ = 20

Then, use the equation to determine the 40th term of the sequence.

Evaluate 5 + 10 + 15 + ... + 245, the total value of the first 49 multiples of five when added altogether.

Determine the missing terms in the given geometric sequence.

81, a₂, a₃, -24

Consider a geometric sequence with a₁ = 245, r = 1/5. Find a₇.