In the previous article, we have discussed Python Program to Find the Sum of Series 9+99+999…..+N

Given a number N and the task is to find the sum of the given series** (3+7+13+21…..+N)** for the given number in Python.

**Examples:**

**Example1:**

**Input:**

Given Number = 9

**Output:**

The total sum of the series till the given number { 9 } = 339

**Example2:**

**Input:**

Given Number = 15

**Output:**

The total sum of the series till the given number { 15 } = 1375

## Program to Find the Sum of Series 3+7+13+21…..+N in Python

Below are the ways to find the sum of the given series** (3+7+13+21…..+N) ** for the given number in Python:

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

**Approach:**

- Give the number N as static input and store it in a variable.
- Take a variable say
**resltsum**which gives the sum of the given series till N and initialize its value to 0. - Loop from 2 to the given number+1 using the for loop.
- Inside the loop, subtract 1 from the iterator value and multiply it with the iterator and add 1 to this result.
- Store it in another variable say
**p**. - Add the value of above
**p**to the above-initialized**resltsum**and store it in the same variable**resltsum.** - Print the
**resltsum**value which is the result of the series till the given Number N. - The Exit of the Program.

**Below is the implementation:**

# Give the number N as static input and store it in a variable. gvn_numb = 9 # Take a variable say resltsum which gives the sum of the given series till N and # initialize its value to 0. resltsum = 0 # Loop from 2 to the given number+1 using the for loop. for itr in range(2, gvn_numb+2): # Inside the loop, subtract 1 from the iterator value and multiply it with the # iterator and add 1 to this result. # Store it in another variable say p. p = 1+(itr*(itr-1)) # Add the value of above p to the above-initialized resltsum and store it in the same # variable resltsum. resltsum += p # Print the resltsum value which is the result of the series till the given Number N. print( "The total sum of the series till the given number {", gvn_numb, "} = ", resltsum)

**Output:**

The total sum of the series till the given number { 9 } = 339

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

**Approach:**

- Give the number N as user input using the int(input()) function and store it in a variable.
- Take a variable say
**resltsum**which gives the sum of the given series till N and initialize its value to 0. - Loop from 2 to the given number+1 using the for loop.
- Inside the loop, subtract 1 from the iterator value and multiply it with the iterator and add 1 to this result.
- Store it in another variable say
**p**. - Add the value of above
**p**to the above-initialized**resltsum**and store it in the same variable**resltsum.** - Print the
**resltsum**value which is the result of the series till the given Number N. - The Exit of the Program.

**Below is the implementation:**

# Give the number N 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 say resltsum which gives the sum of the given series till N and # initialize its value to 0. resltsum = 0 # Loop from 2 to the given number+1 using the for loop. for itr in range(2, gvn_numb+2): # Inside the loop, subtract 1 from the iterator value and multiply it with the # iterator and add 1 to this result. # Store it in another variable say p. p = 1+(itr*(itr-1)) # Add the value of above p to the above-initialized resltsum and store it in the same # variable resltsum. resltsum += p # Print the resltsum value which is the result of the series till the given Number N. print( "The total sum of the series till the given number {", gvn_numb, "} = ", resltsum)

**Output:**

Enter some Random Number = 15 The total sum of the series till the given number { 15 } = 1375

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