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Pi SymbolThe forty trillionth bit of Pi is '0'

Between April 19, 1998, and February 9, 1999, one hundred and twenty-six computers from eighteen different countries set a new record for calculating specific bits of Pi. The previous record of this type was the calculation of the five trillionth bit between March and August 1998, by PiHex.

(Note, the 126 computers is only a small subset of the computers running PiHex -- most people arrived after all the ranges were assigned).

The calculation took a total of about 84,500 cpu hours, and was done using 'idle' time slices (time slices which no other program wants to make use of) under Windows 95 and Windows NT.

The 'average' computer participating was a 200MHz Pentium-based system.

The answer, starting at the 39,999,999,999,997th bit of Pi:

1010 0000 1111 1001 1111 1111 0011 0111 0001 1101
   ^ Forty trillionth bit of Pi
0001 0111 0101 1001 0011 1110 0000
or in hexadecimal, starting at the same point:

Steve Finch has written an article about the BBP formula, (upon which Bellard's formula, is based) and the algorithm of Bailey, Borwein, and Plouffe, which we use.

A good mathematical reference for this topic is the paper which introduced the world for the first time to this type of calculation, written by Bailey, Borwein, and Plouffe. Available in PDF (193K) and Postscript (182K).

Due to the size of the output (many megabytes) produced by PiHex, it is not available for download. It is however available upon request, by contacting Colin Percival.