The formula for the nth triangular number is n(n+1)/2. Therefore, the fourth triangular number is equal to 4 x (4+1) / 2 = (4 x 5) / 2 = 10. The fiftieth triangular number is equal to 50 x (50+1) / 2 = (50 x 51) / 2 = 1275.
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Given a number n, solve the equation x^2 + x - 2n = 0.If n is a triangular number then one solution for x will be a positive integer. Then n is the xth triangular number.
Is 63 a triangular number I think it is a triangular number.
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yes it is a triangular number
No, 18 is not a triangular number.