A109713 - OEIS

%I #14 Jan 28 2025 19:58:46

%S 1,2,4,8,16,20,24,72,200,359,454,624,1054,2060,6301,8083,8407,13159,

%T 65059,74957

%N Numbers n such that 99 * 10^n + 1 is prime.

%C Terms < 21000 have been certified. Primality proof for 13159: PFGW Version 20041001.Win_Stable (v1.2 RC1b) [FFT v23.8] Primality testing 99*10^13159+1 [N-1, Brillhart-Lehmer-Selfridge] Running N-1 test using base 17 Calling Brillhart-Lehmer-Selfridge with factored part 69.89% 99*10^13159+1 is prime! (29.5646s+0.0028s) [Comment edited by _N. J. A. Sloane_, Jan 28 2025]

%H Makoto Kamada, <a href="https://stdkmd.net/nrr/prime/prime_difficulty.txt">Search for 990w1</a>.

%e For n=8 we have 99*10^8+1 = 9900000001, which is prime.

%o (PARI) is(n)=ispseudoprime(99*10^n+1) \\ _Charles R Greathouse IV_, Jun 12 2017

%Y Cf. A056797, A056804, A056805, A056806, A056807.

%K more,nonn

%O 1,2

%A _Jason Earls_, Aug 08 2005

%E Edited by _N. J. A. Sloane_ at the suggestion of Herman Jamke, Jan 13 2008

%E a(19)-a(20) from Kamada data by _Tyler Busby_, Apr 16 2024