19

This number is a prime.

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19 terms are required in the Gregory-Leibniz series, i.e., 4(1 - 1/3 + 1/5 - 1/7 + 1/9 - ...), for the first appearance of "3.1" in the decimal expansion of π. [Honaker]

Submitted: 2007-09-05 20:39:59; Last Modified: 2019-03-14 02:21:31.