No, it is not.
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The explicit formula of a triangular number is:(n + 1 choose 2) which is equivalent to (n + 1)!/(2!(n + 1 - 2)!) = (n + 1)!/(2!(n - 1)!)Assume that 190 is a triangular number. Then:190 = (n + 1)!/(2!(n - 1)!)190 = n(n + 1)/2380 = n(n + 1)380 = n² + n0 = n² + n - 3800 = (n + 20)(n - 19)So n = -20 and n = 19But n has to be positive since n determines the nth triangular number. Therefore, n = 19.Therefore, 19 is a triangular number.
Is 63 a triangular number I think it is a triangular number.
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No, 18 is not a triangular number.
No, 35 is not a triangular number.