Hiya Kotera, (10^23-1)/9 is prime! [N-1, Brillhart-Lehmer-Selfridge] (digits:23) Primeform: CHK:CE16CAB You have correctly spotted patterns there. (10^24-1)/9 is divisible by at least:- 11 111 = 3.37 1111 = 11.101 111111 = 11.(3.37).91; 91=7.13 11111111 = 11.101.10001; 10001=73.137 111111111111 = 111.1111.900991; 900991=7.13.9901 (10^24-1) / (10^12-1) = 10^12+1 10^12+1 = 73.137.99990001 (10^24-1) / (10^8-1) = 10^16+10^8+1 (10^16+10^8+1)/111 = 90090090990991 90090090990991 = 7.13.9901.99990001 Clearly 111111111111/11 = 10101010101 and 111111111111/111 = 1001001001 etc. showing that 2^ab-1 is divisible by 2^a-1 and 2^b-1 and can never therefore be prime, and the same for other bases. People who know more about this than me, forgive me for jumping in first, but it is close to my level of Maths. Cheers, Paul Landon _________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
