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How to check if a number is a triangular number in Python

How to check if a number is a triangular number in Python.

Here's a step-by-step tutorial on how to check if a number is a triangular number in Python:

Step 1: Understand what a triangular number is​

  • A triangular number is a number that can be represented in the form of a triangle, where each row contains an increasing sequence of consecutive numbers.

Step 2: Determine the formula for triangular numbers​

  • The formula to calculate the nth triangular number is (n * (n + 1)) / 2.

Step 3: Create a function to check if a number is triangular​

  • Start by defining a function called is_triangular that takes an integer num as input.

Step 4: Implement the check​

  • Inside the is_triangular function, use a loop to iterate through consecutive numbers starting from 1.
  • For each iteration, calculate the triangular number using the formula mentioned in step 2.
  • Compare the calculated triangular number with the input number num.
  • If the calculated triangular number is equal to num, return True to indicate that the number is triangular.
  • If the calculated triangular number exceeds num, return False to indicate that the number is not triangular.

Step 5: Test the function​

  • After defining the is_triangular function, call it with different numbers to test if it correctly identifies triangular numbers.

Here's an example implementation of the is_triangular function:

def is_triangular(num):
    n = 1
    triangular_num = 1

    while triangular_num < num:
        n += 1
        triangular_num = (n * (n + 1)) / 2

    if triangular_num == num:
        return True
    else:
        return False

To test the function, you can call it with different numbers:

print(is_triangular(6))   # Output: True
print(is_triangular(10))  # Output: False
print(is_triangular(15))  # Output: True

In the above example, is_triangular(6) returns True because 6 is a triangular number, while is_triangular(10) returns False because 10 is not a triangular number. Lastly, is_triangular(15) returns True because 15 is a triangular number.

That's it! You now have a function that can check if a given number is a triangular number in Python.