Changes

==Idea==

==Idea==

Let <math>\text{p}_i\!</math> be the <math>i^\text{th}\!</math> prime, taking <math>2\!</math> as the <math>1^\text{st}\!</math> prime in the sequence that begins as follows:

Let <math>\text{p}_i</math> be the <math>i^\text{th}</math> prime, where <math>i</math> is a positive integer called the ''index'' of the prime  <math>\text{p}_i</math> and the indices are taken such that <math>\text{p}_1 = 2.</math> Thus the sequence <math>\text{p}_i</math> begins as follows:

{| align="center" cellpadding="6" width="90%"

{| align="center" cellpadding="6" width="90%"

\end{matrix}</math>

\end{matrix}</math>

|}

|}

Let <math>I(n)</math> be the set of indices of primes that divide the positive integer <math>n.</math>

Let <math>I(n)</math> be the set of indices of primes that divide the positive integer <math>n.</math>