In this post, We will see how to write a python program for finding Sum of squares of first n natural numbers in different ways.

**Example:**

Input:N = 2Output:1 * 1 + 2 * 2 => 5 OR 1^{2}+ 2^{2}=> 5Input:N = 3Output:1 * 1 + 2 * 2 + 3 * 3 => 14 OR 1^{2}+ 2^{2}+ 3^{2}=> 14

Now, Let’s see the codes:

**Code 1:** Run a loop from 2 to N and for each i, find i ^{ 2 } and adding to the sum.

# first 5 natural numbers N = 5 # initialize variable with 1 sumSquare = 1 # loop from 2 to N for i in range(2, N + 1) : # square summation sumSquare += i ** 2 # print the result print("Sum of the Squares of 1st", N , "Natural Numbers is:",sumSquare)

**Output: **

Sum of the Squares of 1st 5 Natural Numbers is: 55

**Code 2:** Create user defined function, main and then apply the previous code logic.

# Define a user defined # function for finding # sum of squares of 1st # N natural Numbers def sumOfSquares(Num) : # initialize variable with 1 sumSquare = 1 # loop from 2 to N for i in range(2, Num + 1) : # square summation sumSquare += i ** 2 # return result return sumSquare # main code if __name__ == "__main__" : # first 5 natural numbers Num = 5 # function calling and # printing the result print("Sum of the Squares of first", Num , "Natural Numbers is:", sumOfSquares(Num))

**Output: **

Sum of the Squares of first 5 Natural Numbers is: 55

**Code 3:** Run a loop from 2 to N and for each i, find i * i and adding to the sum.

# Define a user defined # function for finding # sum of squares of 1st # N natural Numbers def sumOfSquares(Num) : # initialize variable with 1 sumSquare = 1 # loop from 2 to N for i in range(2, Num + 1) : # square summation sumSquare += i * i # return result return sumSquare # main code if __name__ == "__main__" : # first 5 natural numbers Num = 5 # function calling and # printing the result print("Sum of the Squares of 1st", Num , "Natural Numbers is:", sumOfSquares(Num))

**Output: **

Sum of the Squares of 1st 5 Natural Numbers is: 55

**Code 4:** By Using given formula :

sum of the squares of 1st N Natural numbers:((N) * (N + 1) * (2 * N + 1)) / 6

# Define a user defined # function for finding # sum of squares of 1st # N natural Numbers def sumOfSquares(Num) : # return result return ((Num) * (Num + 1) * (2 * Num + 1)) / 6 # main code if __name__ == "__main__" : # first 5 natural numbers Num = 5 # function calling and # printing the result print("Sum of the Squares of 1st", Num , "Natural Numbers is:", sumOfSquares(Num))

**Output: **

Sum of Squares of first 5 Natural Numbers is: 55

**Code 5:** By making a anonymous function.

# create a annonymous # function for returning # sum of squares of 1st # N natural Numbers sumOfSquares = lambda Num : ((Num) * (Num + 1) * (2 * Num + 1)) / 6 # main code if __name__ == "__main__" : # first 5 natural numbers Num = 5 # function calling and # printing the result print("Sum of the Squares of 1st", Num , "Natural Numbers is:", sumOfSquares(Num))

**Output: **

Sum of the Squares of 1st 5 Natural Numbers is: 55