Harmonic series
= Harmonic series
{title2=$\sum_{n=1}^{\infty}\frac1n$}
{wiki}
The harmonic series diverges. Grouping terms from $2^k+1$ through $2^{k+1}$ gives at least $2^k/2^{k+1}=1/2$ from every block.
= Harmonic series
{title2=$\sum_{n=1}^{\infty}\frac1n$}
{wiki}
The harmonic series diverges. Grouping terms from $2^k+1$ through $2^{k+1}$ gives at least $2^k/2^{k+1}=1/2$ from every block.