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Old 2022-02-08, 05:20   #2
sweety439
 
"99(4^34019)99 palind"
Nov 2016
(P^81993)SZ base 36

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Quote:
Originally Posted by carpetpool View Post
and find that 2^n-1 is prime for n = 2, 3, 5, 7, 11, 13, 17, 19, 31, 61, 89. The first 6 terms are a trivial result of dividing 2^n-1 by all prime factors of the form 2*k*n+1, with k > l, and 2*l*n+1 > 2^n-1. The others are a result of a primality test after 'sieving'. Other large sequences should work the same way, leaving less primes indices n to test in S(n).
2^11-1 = 23 * 89 is composite
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