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 A114247 #22 Feb 16 2025 08:32:59
%S A114247 1,1,5,20,73,248,745,1954,5239,13837,36042,92893
%N A114247 Number of Fermat pseudoprimes to base 5 less than 10^n.
%H A114247 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/FermatPseudoprime.html">Fermat Pseudoprime</a>
%H A114247 <a href="/index/Ps#pseudoprimes">Index entries for sequences related to pseudoprimes</a>
%t A114247 Table[Count[Select[Range[2, 10^6], ! PrimeQ[#] && PowerMod[5, # - 1, #] == 1 &], x_ /; x < 10^n], {n, 6}] (* _Robert Price_, Jun 09 2019 *)
%Y A114247 Cf. A005936, A114245, A114249.
%K A114247 nonn,more
%O A114247 1,3
%A A114247 _Eric W. Weisstein_, Nov 18 2005
%E A114247 a(9)-a(12) from _Hiroaki Yamanouchi_, Sep 25 2015