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 A243292 #9 Sep 08 2022 08:46:08 %S A243292 5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,85,89, %T A243292 91,97,101,103,107,109,113,127,131,137,139,149,151,157,163,167,173, %U A243292 179,181,191,193,197,199,211,223,227,229,233,239,241,251,257,263,269,271 %N A243292 Odd numbers n such that (4^n - 1)/3 is a base-2 pseudoprime. %C A243292 Odd numbers not divisible by 3 that are primes or pseudoprimes to base 4. %H A243292 Wikipedia, <a href="http://en.wikipedia.org/wiki/Fermat_pseudoprime">Fermat pseudoprime</a> %H A243292 <a href="/index/Ps#pseudoprimes">Index entries for sequences related to pseudoprimes</a> %o A243292 (Magma) [n: n in [1..271 by 2] | not n mod 3 eq 0 and IsOne(4^(n-1) mod n)]; %Y A243292 Cf. A000040, A001567, A020136, A210454. %K A243292 nonn %O A243292 1,1 %A A243292 _Arkadiusz Wesolowski_, Jun 02 2014