Stage: 5 Challenge Level: 
Prove that the sum of the reciprocals of the first $n$ triangular numbers gets closer and closer to $2$ as $n$ grows.
Manipulating algebraic expressions/formulae. Inequality/inequalities. Stage 5 - Reviewed 2012. Summation of series. epsilons. alphas. Mathematical reasoning & proof. Powers & roots. Triangle numbers. Limits.
Published September 2001.
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