Hello, there are many ways to reformulate the original series for Pi : inf 4 2 1 1 -k pi = sum (---- - ---- - ---- - ----) 16 k=0 8k+1 8k+4 8k+5 8k+6 the original finding on sept 19, 1995 was actualy different : Pi = 4*f(1/4) + 2 arctan (1/2) - log(5) where f(1/4) = sum((-1)^(n+1)/(4*n+1),n=1..infinity) OR f(1/4) = 2F2(1,1/4; 5/4; -1/4) another formulation found that same day was also : Pi = sum(c(n)/16^floor(n/8)/n,n=0..infinity) where c(n) = {4,0,0,-2, -1, -1, 0, 0} and periodic. The published formula for pi, called the BBP formula was re-arranged by Peter Borwein, 2 days after the initial discovery. <we> kept that one to be published, the rest of the story for the discovery was posted by me on june 23, 2003 for personal reasons on sci.math. Simon Plouffe