What is the term for the sequence of six 9s in pi that Richard Feynman noted?

The sequence of six 9s in pi is called the Feynman point. It begins at the 762nd digit after the decimal point in pi, where the expansion contains 999999.

The name comes from a story that Richard Feynman said he wanted to memorize pi up to that point so he could recite it and make the number appear to end with six 9s. That joke would humorously suggest that pi was rational, even though pi is irrational and its decimal expansion never terminates or repeats in a fixed cycle.

The coincidence is mathematically notable because six identical digits appear relatively early in pi's decimal expansion. The next run of six consecutive identical digits is another sequence of 9s, beginning at position 193,034.

The attribution to Feynman is not fully secure. The story is not found in his memoirs or known biographies, and the earliest documented mention of the idea is associated with Douglas Hofstadter's 1985 book Metamagical Themas. Nevertheless, “Feynman point” is the established name.