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")