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Old 2018-10-06, 02:48   #11
Romulan Interpreter
LaurV's Avatar
Jun 2011

22·2,341 Posts

Originally Posted by MisterBitcoin View Post
Not actually related to CRUS, but still interesting:
Primes for form 172*3^n+1
These are all primes n<25000.
Not going deeper, atm.
I still don't get it what is interesting about primes that can be found in less than half hour of pari/gp one-liner run? [/end of Sat_morning_grumpy_because_not_yet_coffee]

gp > for(n=1,50000,if(isprime(172*3^n+1),print("prime for: "n),printf("...%d...%c",n,13)))
prime for: 2
prime for: 4
prime for: 22
prime for: 25
prime for: 34
prime for: 44
prime for: 49
prime for: 54
prime for: 57
prime for: 114
prime for: 142
prime for: 265
prime for: 328
prime for: 360
prime for: 453
prime for: 520
prime for: 764
prime for: 1070
prime for: 2200
prime for: 3424
  ***   at top-level: for(n=1,50000,if(isprime(172*3^n+1),p
  ***                                  ^--------------------
  *** isprime: user interrupt after 1min, 31,719 ms
  ***   Break loop: <Return> to continue; 'break' to go back to GP prompt
(this is a slow laptop, which is factoring aliquotes in parallel, and yes, I understand that it gets slower and slower as it comes to higher n, without any sieving, but please come back with some 400k+ digits primes of this form, and then we talk...)

Going for that coffee... the machine is beeping...
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