# 16th April

On this day in 1673, Leibniz wrote to Oldenburg about series:-

I conjecture that Mr Collins himself does not speak of these summations of infinite series because he brings forward the example of the series $\large\frac 1 2\normalsize, \large\frac 1 3\normalsize, \large\frac 1 4\normalsize, \large\frac 1 5\normalsize, \large\frac 1 6\normalsize, ...$ which if it is continued to infinity cannot be summed because the sum is not finite, like the sum of the triangular numbers, but infinite. But now I am cramped by the space of my paper.On this day in 2009 Google released a Huygens doodle (two days late).