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 A090082 #17 Mar 31 2024 02:08:14
%S A090082 4,124,5662,11476,59356,80476,91636,250876,261964,482516,1385836,
%T A090082 1892458,1926676,2428084,2589796,3743476,4101796,6797764,9155476,
%U A090082 10701076,10743436,11263396,13799836,13859956,15570556,20396476
%N A090082 Even pseudoprimes to base 5.
%H A090082 Amiram Eldar, <a href="/A090082/b090082.txt">Table of n, a(n) for n = 1..910</a> (terms below 10^12, calculated from the b-file at A005936; terms 1..100 from Charles R Greathouse IV)
%H A090082 <a href="/index/Ps#pseudoprimes">Index entries for sequences related to pseudoprimes</a>.
%t A090082 Do[s=Mod[ -1+5^(n-1), n]; If[Equal[s, 0]&&!PrimeQ[n]&&EvenQ[n], Print[n]], {n, 1, 1000000}]
%o A090082 (PARI) is(n)=Mod(5,n)^(n-1)==1&&!isprime(n)&&n%2==0 \\ _Charles R Greathouse IV_, Apr 12 2012
%o A090082 (PARI) p=2;forprime(q=3,1e8,forstep(n=p+1,q-1,2,if(Mod(5,n)^(n-1)==1,print1(n", ")));p=q) \\ _Charles R Greathouse IV_, Apr 12 2012
%Y A090082 Cf. A005936.
%K A090082 nonn
%O A090082 1,1
%A A090082 _Labos Elemer_, Nov 25 2003
%E A090082 More terms from _Farideh Firoozbakht_, Sep 13 2006