44444...44449 (48-digits)

This number is a prime.

                        44444444 4444444444 4444444444 4444444444 4444444449

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The largest prime among the initial one hundred terms in the almost repunit sequence 9, 49, 449, 4449, 44449, etc. The closed formula for this sequence is given by f (n) = (4 * 10 ^ n + 41) / 9 while a recursive formula is furnished as follows: Define u (1) = 9 while u (n) = 10 * u (n - 1) - 41. [Schiffman]