 In order to render the case more simple I will suppose that A throw in the air a piece of money, B undertakes to give him a coin, if the side of Heads falls on the first toss, 2, if it is only the second, 4, if it is the 3rd toss, 8, if it is the 4th toss, etc. The paradox consists in this that the calculation gives for the equivalent that A must give to B an infinite sum, which would seem absurd. (Cramér to N. Bernoulli, 21 May 1728)