Let <math>\text{p}_i\!</math> be the <math>i^\text{th}\!</math> prime, taking <math>2\!</math> as <math>1^\text{st}\!</math> prime in the sequence that begins as follows:
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: <math>\text{p}_1 = 2, \text{p}_2 = 3, \text{p}_3 = 5, \text{p}_4 = 7, \text{p}_5 = 11\!</math> and so on.