What is the sum of the series -LSB- math -RSB- 1 + 1 / 2 + 1 / 3 + 1 / 4 + 1 / 5 ... -LSB- / math -RSB- up to infinity ? How can it be calculated ?
How does one calculate the sum : 1/2 * 3 + 1/3 * 4 + 1/4 * 5 + ... + 1/48 * 49 + 1/49 * 50 ?