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 A114245 #34 Feb 16 2025 08:32:59
%S A114245 0,1,6,23,78,246,760,2155,5804,15472,39871,102839,264461
%N A114245 Number of Fermat pseudoprimes to base 3 less than 10^n.
%H A114245 Michal Mikuš, <a href="https://folk.ntnu.no/skoge/prost/proceedings/slovak_control_conference_2010/pdf/31_Mikus.pdf">Computing the Pseudoprimes up to 10^13</a>, Cybernetics and Informatics, International Conference SSKI, February 10-13, 2010.
%H A114245 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/FermatPseudoprime.html">Fermat Pseudoprime</a>.
%H A114245 <a href="/index/Ps#pseudoprimes">Index entries for sequences related to pseudoprimes</a>.
%F A114245 A005935(a(n)) < 10^n; A005935(a(n)+1) > 10^n. - _R. J. Mathar_, Feb 10 2007
%t A114245 Table[Count[Select[Range[2, 10^6], ! PrimeQ[#] && PowerMod[3, # - 1, #] == 1 &], x_ /; x < 10^n], {n, 6}] (* _Robert Price_, Jun 09 2019 *)
%o A114245 (PARI) isFps(n,b)= { if(isprime(n), return(0) ) ; if( (b^(n-1)) % n == 1, return(1), return(0) ) ; } { a=0 ; e=1 ; for(n=1,10^12, if( n == 10^e, e++ ; print(a) ; ) ; a += isFps(n,3) ; ) ; } \\ _R. J. Mathar_, Feb 10 2007
%Y A114245 Cf. A005935, A114247, A114249.
%K A114245 nonn,more
%O A114245 1,3
%A A114245 _Eric W. Weisstein_, Nov 18 2005
%E A114245 a(9)-a(10) from _Washington Bomfim_, Mar 02 2012
%E A114245 a(11)-a(12) from _Hiroaki Yamanouchi_, Sep 25 2015
%E A114245 a(13) from Mikuš (2010) added by _Amiram Eldar_, Mar 31 2024