- #1

arydberg

- 244

- 31

I would like to point out that a sieve may be used to block out many non prime Mersenne numbers.

For example for n = 2 x = 3 but on closer inspection every even value of n other than n = 2 is non prime furthermore they are all divisible by 3, Thus we can cross out n=4, n=6, … up to n=38.

Also starting at n=3 and x = 7 we find that every third number larger than 3 is divisible by 7 so we could cross out n = 6, n=9, n=12 … up to n = 39.

Now let's move to n=5 or x = 31. now we can cross out every fifth number larger than n=5 as they are all divisible by 31

if we move to n=7 and x = 127 we find that every 7th number larger than 7 is divisible by 127 and can be crossed out.

11 should be crossed off as 2047 is not prime

My question is does this go on forever and can we use it to delete many Mersenne numbers as non primes.

The next prime is 11

n 2^n - 1

n = 1 x = 1

n = 2 x = 3

n = 3 x = 7

n = 4 x = 15

n = 5 x = 31

n = 6 x = 63

n = 7 x = 127

n = 8 x = 255

n = 9 x = 511

n = 10 x = 1023

n = 11 x = 2047

n = 12 x = 4095

n = 13 x = 8191

n = 14 x = 16383

n = 15 x = 32767

n = 16 x = 65535

n = 17 x = 131071

n = 18 x = 262143

n = 19 x = 524287

n = 20 x = 1048575

n = 21 x = 2097151

n = 22 x = 4194303

n = 23 x = 8388607

n = 24 x = 16777215

n = 25 x = 33554431

n = 26 x = 67108863

n = 27 x = 134217727

n = 28 x = 268435455

n = 29 x = 536870911

n = 30 x = 1073741823

n = 31 x = 2147483647

n = 32 x = 4294967295

n = 33 x = 8589934591

n = 34 x = 17179869183

n = 35 x = 34359738367

n = 36 x = 68719476735

n = 37 x = 137438953471

n = 38 x = 274877906943

n = 39 x = 549755813887