### Home > A2C > Chapter 9 > Lesson 9.1.2 > Problem9-43

9-43.

A sequence of pentagonal numbers is started below.

1. Find the next three pentagonal numbers.

$13, 17, 21$What kind of sequence do the pentagonal numbers form?

2. What is the equation for the nth pentagonal number?

Is a constant being added to each number to obtain the next? Multiplied? Neither?

3. What is the equation for the $n^{th}$ pentagonal number?

$t\left(n\right) = 4n − 3$