Using his company’s distributed computing facilities, Tsz-Wo Sze, a Yahoo! researcher, has computed a sequence of binary digits of pi beginning at the two quadrillionth binary digit of pi. This computation used Bellard’s variant of the original “BBP” formula for pi, which formula was discovered in 1996 by a computer program running the “PSLQ” integer relation algorithm.
A New Scientist article describing this computation is available here: New Scientist.
A paper written by Sze presenting the details of his computational methods and results is available here: Sze manuscript.
Additional background information on the history of pi and the BBP formula for pi is available here: “The Life of Pi” and “The Quest for Pi”.