In the previous article, we have discussed Python Program to Print Series 1, 3, 7, 15, 31 … N

Given a number N and the task is to print the series** (1, -2, 6, -15, 31 … N)** till the given number N in Python.

**Examples:**

**Example1:**

**Input:**

Given Number (Limit) = 8

**Output:**

The above series till the given number{ 8 } is : 1 -2 6 -15 31 -56 92 -141

**Example2:**

**Input:**

Given Number (Limit) = 11

**Output:**

The above series till the given number{ 11 } is : 1 -2 6 -15 31 -56 92 -141 205 -286 386

## Program to Print Series 1, -2, 6, -15, 31 … N in Python

Below are the ways to print the series** (1, -2, 6, -15, 31 … N)** till the given number N in Python :

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

**Approach:**

- Give the number N (Limit) as static input and store it in a variable.
- Take a variable to say
**itr**and initialize its value to 1. - Take another variable say
**previous_val**and initialize its value to 1. - Loop until the above-declared variable itr value is less than or equal to the given number using the while loop.
- Inside the loop, check if the above itr value is even or not using the if conditional statement.
- If it is true, then print the value of above
**previous_val**multiplied with -1 separated by spaces. - Else, Print the value of the above
**previous_val**separated by spaces. - Calculate the value of itr raised to power 2 using the pow() function and add it to the
**previous_val.** - Store it in the same variable
**previous_val.** - Increment the above
**itr**value by 1. - The Exit of the Program.

**Below is the implementation:**

# Give the number N (Limit) as static input and store it in a variable. gvn_numb = 8 # Take a variable to say itr and initialize its value to 1. itr = 1 # Take another variable say previous_val and initialize its value to 1. previous_val = 1 print("The above series till the given number{", gvn_numb, "} is :") # Loop until the above-declared variable itr value is less than or equal to the # given number using the while loop. while itr <= gvn_numb: # Inside the loop, check if the above itr value is even or not using the if # conditional statement. if(itr % 2 == 0): # If it is true, then print the value of above previous_val multiplied with -1 # separated by spaces. print(-1*previous_val, end=" ") else: # Else, Print the value of the above previous_val separated by spaces. print(previous_val, end=" ") # Calculate the value of itr raised to power 2 using the pow() function and # add it to the previous_val. # Store it in the same variable previous_val. previous_val += pow(itr, 2) # Increment the above itr value by 1. itr += 1

**Output:**

The above series till the given number{ 8 } is : 1 -2 6 -15 31 -56 92 -141

### Method #2: Using While loop (User Input)

**Approach:**

- Give the number N (Limit) as user input using the int(input()) function and store it in a variable.
- Take a variable to say
**itr**and initialize its value to 1. - Take another variable say
**previous_val**and initialize its value to 1. - Loop until the above-declared variable itr value is less than or equal to the given number using the while loop.
- Inside the loop, check if the above itr value is even or not using the if conditional statement.
- If it is true, then print the value of above
**previous_val**multiplied with -1 separated by spaces. - Else, Print the value of the above
**previous_val**separated by spaces. - Calculate the value of itr raised to power 2 using the pow() function and add it to the
**previous_val.** - Store it in the same variable
**previous_val.** - Increment the above
**itr**value by 1. - The Exit of the Program.

**Below is the implementation:**

# Give the number N (Limit) as user input using the int(input()) function and # store it in a variable. gvn_numb = int(input("Enter some Random Number = ")) # Take a variable to say itr and initialize its value to 1. itr = 1 # Take another variable say previous_val and initialize its value to 1. previous_val = 1 print("The above series till the given number{", gvn_numb, "} is :") # Loop until the above-declared variable itr value is less than or equal to the # given number using the while loop. while itr <= gvn_numb: # Inside the loop, check if the above itr value is even or not using the if # conditional statement. if(itr % 2 == 0): # If it is true, then print the value of above previous_val multiplied with -1 # separated by spaces. print(-1*previous_val, end=" ") else: # Else, Print the value of the above previous_val separated by spaces. print(previous_val, end=" ") # Calculate the value of itr raised to power 2 using the pow() function and # add it to the previous_val. # Store it in the same variable previous_val. previous_val += pow(itr, 2) # Increment the above itr value by 1. itr += 1

**Output:**

Enter some Random Number = 11 The above series till the given number{ 11 } is : 1 -2 6 -15 31 -56 92 -141 205 -286 386

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