Python Check If Number Is Triangle Number

Python program to check if number is triangle number.

# ? 2017 TheFlyingKeyboard and released under MIT License
# theflyingkeyboard.net

def isSquare(n):
    if n < 1:
        return False
    else:
        for i in range(0, int(n/2) + 2):
            if (i * i) == n:
                return True
        return False

num = int(input("Enter a number:"))

if isSquare(8 * num + 1):
  print("Number is triangle number")
else:
  print("Number is not triangle number")