99999...99991 (45-digits)

This number is a prime.

                           99999 9999999999 9999999999 9999999999 9999999991

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The largest prime output among the initial one hundred terms in the almost repunit sequence 1, 91, 991, 9991, 99991, etc. The closed formula for this sequence can be given as follows: f (n) = 10 ^ n - 9 and a recursive formula can be defined by setting u (1) = 1 and u (n) = 10 * u (n - 1) + 81 for n > 1. [Schiffman]