Given the number N, the task is to print the first n numbers of the pell series in Python.

**Pell Series:**

The Pell Series is a series in which the next number equals the sum of twice the previous number and the number preceding the previous number.

It begins with 1 and 2.

Pell Numbers: 1,2,5,12,29,70,169,…

Consider the following number sequence and try to match it to the definition of the Pell Series:

1 + 2 x 2 = 5

2 + 5* 2 = 12

5 + 12 x 2 = 29

12 + 29*2 = 70

29 + 70*2 = 169

and so onâ€¦

Now that you have a clear idea of what the Pell Series are, letâ€™s move on to how we shall write the Python code to generate the same.

**Examples:**

**Example1:**

Given number = 12

**Input:**

The first 12 numbers of the pell series are : 1 2 5 12 29 70 169 408 985 2378 5741 13860

**Output:**

**Example2:**

**Input:**

Given number = 21

**Output:**

The first 21 numbers of the pell series are : 1 2 5 12 29 70 169 408 985 2378 5741 13860 33461 80782 195025 470832 1136689 2744210 6625109 15994428 38613965

## Program to Generate first N numbers of Pell Series in Python

Below are the ways to generate the first N number of the pell series in Python.

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### Method #1: Using For Loop (Static Input)

**Approach:**

- Give the number N as static input and store it in a variable.
- Take a variable temp1 and initialize it to 1.
- Take another variable temp2 and initialize it to 2.
- Take the third variable temp3 and initialize it to 0.
- Now, print the first two numbers in the series, and we’ll print the other generated numbers in the order they were generated.
- Loop till number -2 using For loop.
- Add the value of temp1 and twice the temp2 value and initialize the temp3 with this value.
- Swap the previous number for the previous number’s predecessor (temp1 =temp2).
- Swap the generated and previously generated numbers (temp2 = temp3).
- Print the value of temp3.
- The Exit of the Program.

**Below is the implementation:**

# Give the number N as static input and store it in a variable. numb = 21 # Take a variable temp1 and initialize it to 1. temp1 = 1 # Take another variable temp2 and initialize it to 2. temp2 = 2 # Take the third variable temp3 and initialize it to 0. temp3 = 0 # Now, print the first two numbers in the series, # and we'll print the other generated numbers in the order they were generated. print('The first', numb, 'numbers of the pell series are :') print(temp1, temp2, end=' ') # Loop till number -2 using For loop. for i in range(numb-2): # Add the value of temp1 and twice the temp2 value # and initialize the temp3 with this value. temp3 = temp1+2*temp2 # Swap the previous number for the previous number's predecessor (temp1 =temp2). temp1 = temp2 # Swap the generated and previously generated numbers (temp2 = temp3) temp2 = temp3 # Print the value of temp3. print(temp3, end=' ')

**Output:**

The first 21 numbers of the pell series are : 1 2 5 12 29 70 169 408 985 2378 5741 13860 33461 80782 195025 470832 1136689 2744210 6625109 15994428 38613965

### Method #2: Using For Loop (User Input)

**Approach:**

- Give the number N as user input using int(input()) and store it in a variable.
- Take a variable temp1 and initialize it to 1.
- Take another variable temp2 and initialize it to 2.
- Take the third variable temp3 and initialize it to 0.
- Now, print the first two numbers in the series, and we’ll print the other generated numbers in the order they were generated.
- Loop till number -2 using For loop.
- Add the value of temp1 and twice the temp2 value and initialize the temp3 with this value.
- Swap the previous number for the previous number’s predecessor (temp1 =temp2).
- Swap the generated and previously generated numbers (temp2 = temp3).
- Print the value of temp3.
- The Exit of the Program.

**Below is the implementation:**

# Give the number N as user input using int(input()) and store it in a variable. numb = int(input('Enter some random number = ')) # Take a variable temp1 and initialize it to 1. temp1 = 1 # Take another variable temp2 and initialize it to 2. temp2 = 2 # Take the third variable temp3 and initialize it to 0. temp3 = 0 # Now, print the first two numbers in the series, # and we'll print the other generated numbers in the order they were generated. print('The first', numb, 'numbers of the pell series are :') print(temp1, temp2, end=' ') # Loop till number -2 using For loop. for i in range(numb-2): # Add the value of temp1 and twice the temp2 value # and initialize the temp3 with this value. temp3 = temp1+2*temp2 # Swap the previous number for the previous number's predecessor (temp1 =temp2). temp1 = temp2 # Swap the generated and previously generated numbers (temp2 = temp3) temp2 = temp3 # Print the value of temp3. print(temp3, end=' ')

**Output:**

Enter some random number = 12 The first 12 numbers of the pell series are : 1 2 5 12 29 70 169 408 985 2378 5741 13860

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