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 A188803 #35 Jul 07 2023 09:55:49
%S A188803 3,17,257,641,65537,167772161,2748779069441,46179488366593,
%T A188803 1328165573307087716353,188894659314785808547841
%N A188803 Primes that divide 2^(2^100) - 1 and 10^(10^100) - 1.
%C A188803 Probably there are no more terms. [_Arkadiusz Wesolowski_, Jul 12 2011]
%H A188803 Dario A. Alpern, <a href="https://www.alpertron.com.ar/googolm1.pl">Known prime factors of Googolplex - 1</a>
%H A188803 G. L. Honaker, Jr. and Chris Caldwell, <a href="https://t5k.org/curios/cpage/5833.html">Prime Curios! 167772161</a>
%H A188803 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/FermatNumber.html">Fermat Number</a>
%H A188803 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Googolplex.html">Googolplex</a>
%H A188803 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/GreatestCommonDivisor.html">Greatest Common Divisor</a>
%t A188803 Select[Sort[Flatten[Table[z = k*2^n + 1; If[PowerMod[2, 2^100, z] == PowerMod[10, 10^100, z] == 1, z], {k, 1, 21, 2}, {n, 75}]]], PrimeQ] (* _Arkadiusz Wesolowski_, Sep 08 2011 *)
%Y A188803 Cf. A023394.
%K A188803 fini,full,nonn
%O A188803 1,1
%A A188803 _Arkadiusz Wesolowski_, Apr 12 2011