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Math Help - Triangular Factorials proof

  1. #1
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    Triangular Factorials proof

    Hello everyone.

    I came across this statement and have been looking for a proof. Can anyone help me out?

    Prove that 1, 6 and 120 are the only numbers which are both triangular and factorials.
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  2. #2
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    Quote Originally Posted by obinnaokechukwu View Post
    Hello everyone.

    I came across this statement and have been looking for a proof. Can anyone help me out?

    Prove that 1, 6 and 120 are the only numbers which are both triangular and factorials.

    Here's a clue: the nth triangluar number is given by [tex] \frac{n(n+1)}{2}[\math]
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