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Numbers n such that 55*10^n + 1 is prime.
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%I #9 Apr 24 2024 07:34:20

%S 2,3,7,9,33,61,93,112,284,615,1293,2558,2925,5961,6454,7960,17521,

%T 40838

%N Numbers n such that 55*10^n + 1 is prime.

%C All values proved prime. No more up to 25000. Primality proof for the largest: PFGW Version 20041001.Win_Stable (v1.2 RC1b) [FFT v23.8] Primality testing 55*10^17521+1 [N-1, Brillhart-Lehmer-Selfridge] Running N-1 test using base 3 Calling Brillhart-Lehmer-Selfridge with factored part 69.89% 55*10^17521+1 is prime! (48.1892s+0.1481s)

%o (PARI) is(n)=ispseudoprime(55*10^n+1) \\ _Charles R Greathouse IV_, Jun 13 2017

%Y Cf. A056806, A056805.

%K more,nonn

%O 1,1

%A _Jason Earls_, Aug 15 2005

%E a(18) from Kamada data by _Tyler Busby_, Apr 24 2024