This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A109800 #9 Apr 24 2024 07:34:20 %S A109800 2,3,7,9,33,61,93,112,284,615,1293,2558,2925,5961,6454,7960,17521, %T A109800 40838 %N A109800 Numbers n such that 55*10^n + 1 is prime. %C A109800 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 A109800 (PARI) is(n)=ispseudoprime(55*10^n+1) \\ _Charles R Greathouse IV_, Jun 13 2017 %Y A109800 Cf. A056806, A056805. %K A109800 more,nonn %O A109800 1,1 %A A109800 _Jason Earls_, Aug 15 2005 %E A109800 a(18) from Kamada data by _Tyler Busby_, Apr 24 2024