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 A185084 #17 Jul 18 2021 04:33:49
%S A185084 0,0,0,0,0,0,2,2,3,6,10,17,21,30,44,61,87,124,175,254,362,511,696,955,
%T A185084 1313,1802,2462,3321,4422,5969,8089,10785,14513,19333,25774,34259,
%U A185084 45522
%N A185084 Number of Fermat pseudoprimes to base 3 less than 2^n.
%e A185084 a(1) = a(2) = ... = a(6) = 0 because A005935(1) = 91 > 2^6.
%e A185084 a(7) = 2 since A005935(1) = 91, A005935(2) = 121, A005935(3) = 286, and 121 < 2^7 < 286.
%t A185084 cnt = 0; Table[Do[If[! PrimeQ[i] && PowerMod[3, i-1, i] == 1, cnt++], {i, 2^(n-1) + 1, 2^n}]; cnt, {n, 20}] (* _T. D. Noe_, Mar 02 2012 *)
%Y A185084 Cf. A005935, A114245.
%K A185084 nonn,more
%O A185084 1,7
%A A185084 _Washington Bomfim_, Mar 02 2012
%E A185084 a(35)-a(37) from _Amiram Eldar_, Jul 18 2021