Six nines in pi

A sequence of six consecutive nines occurs in the decimal representation of the number pi (π), starting at the 762nd decimal place.[1][2] It has become famous because of the mathematical coincidence, and because of the idea that one could memorize the digits of π up to that point, and then suggest that π is rational. The earliest known mention of this idea occurs in Douglas Hofstadter's 1985 book Metamagical Themas, where Hofstadter states[3][4]

I myself once learned 380 digits of π, when I was a crazy high-school kid. My never-attained ambition was to reach the spot, 762 digits out in the decimal expansion, where it goes "999999", so that I could recite it out loud, come to those six 9s, and then impishly say, "and so on!"

This sequence of six nines is colloquially known as the "Feynman point",[5] after physicist Richard Feynman, who allegedly stated this same idea in a lecture.[6] However it is not clear when, or even if, Feynman ever made such a statement. It is not mentioned in published biographies (viz. James Gleick) or his own memoirs. [7]

  1. ^ Wells, D. (1986), The Penguin Dictionary of Curious and Interesting Numbers, Middlesex, England: Penguin Books, p. 51, ISBN 0-14-026149-4.
  2. ^ "A048940 - OEIS". oeis.org. Retrieved 1 May 2023.
  3. ^ Hofstadter, Douglas (1985). Metamagical Themas. Basic Books. ISBN 0-465-04566-9.
  4. ^ Rucker, Rudy (5 May 1985). "Douglass Hofstadter's Pi in the Sky". The Washington Post. Archived from the original on 13 July 2017. Retrieved 4 January 2016.
  5. ^ Weisstein, Eric W. "Feynman Point". mathworld.wolfram.com. Retrieved 1 May 2023.
  6. ^ Arndt, J. & Haenel, C. (2001), Pi – Unleashed, Berlin: Springer, p. 3, ISBN 3-540-66572-2.
  7. ^ David Brooks (12 January 2016). "Wikipedia turns 15 on Friday (citation needed)". Concord Monitor. Archived from the original on 18 January 2017. Retrieved 10 February 2016.