44444...44449 (48-digits)

This number is a prime.

                        44444444 4444444444 4444444444 4444444444 4444444449

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]