The sequences in Exercises 13–18 are defined using recursion formulas. Write the first four terms of each sequence. a₁=4 and a_n=2a_n-1 + 3 for n≥2

In Exercises 19–22, the general term of a sequence is given and involves a factorial. Write the first four terms of each sequence. a_n = n²/n!

In Exercises 19–22, the general term of a sequence is given and involves a factorial. Write the first four terms of each sequence. a_n=2(n+1)!

Evaluate each factorial expression. 17!/15!

Evaluate each factorial expression. (n+2)!/n!

Find each indicated sum. ${\sum }_{i=1}^{6}5i$

Find each indicated sum. ${\sum }_{i=1}^{4}2i^2$

Find each indicated sum. ${\sum }_{k=1}^{5}k(k+4)$