What do you call the terms between two nonconsecutive terms of an arithmetic sequence?

What is the value of a₁ in the sequence 4, 9, 14, 19,... ?

In an arithmetic sequence defined as a_n = a₁ + (n – 1)d, what do you call d ?

It is a sequence where each term after the first is obtained by multiplying the preceding term by the same constant.

If the arithmetic sequence has a common difference, then the geometric sequence has a common ____:

What do you call special type of mean where we multiply the terms together and then take a square root (for two terms), cube root (for three terms) etc?

What is the next term in geometric sequence 5,10,20,__?

What is the next term of the sequence 1,4,9,16,...?

Determine the 5^th term of the sequence given the nth term a_n = 3n – 4.