Riesel primes of the form 391581•2n-1

Current data

k , b : 391581 , 2 Type : 3 Count : 42 Nash : 2267 Max n : 4,000,000 Date : 2024-07-06

7, 14, 41, 53, 71, 173, 194, 334, 473, 994, 1489, 1919, 2047, 2399, 2501, 2825, 4145, 4867, 5026, 5555, 5569, 5834, 22778, 27229, 29846, 34109, 39383, 51926, 56690, 61205, 212173, 216193, 219371, 234725, 258493, 572861, 952054, 1189658, 1210958, 1852685, 2217203, 2284871

Remarks :

391581*2^216193-1 was the largest known prime from 1989-08-06 to 1992-02-19 and the only largest non-Mersenne prime since 1951. See additional info at Amdahl Six and Landon Noll's page.

History

• 2024-07-06: Checked n = 200000 - 4000000, Ryan Propper, double-check n = 200000 - 300000
• 2024-07-06: Found n = 2284871, Ryan Propper
• 2024-07-06: Found n = 2217203, Ryan Propper
• 2024-06-25: Checked n = 1 - 300000, Gary Barnes, released
• 1989-08-06: Found n = 216193, John Brown, Landon Curt Noll, Bodo Parady, Gene Smith, Joel Smith, Sergio Zarantonello, Amdahl Six