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 A262052 #37 Jun 29 2019 10:19:05
%S A262052 217,781,1541,1729,5461,5611,6601,7449,7813,11041,12801,13021,13333,
%T A262052 14981,15751,15841,16297,21361,23653,24211,25351,29539,30673,38081,
%U A262052 40501,41041,44173,44801,46657,47641,48133,53971,56033,67921,75361,79381,90241,98173,100651,102311
%N A262052 Euler pseudoprimes to base 5: composite integers such that abs(5^((n - 1)/2)) == 1 mod n.
%H A262052 Amiram Eldar, <a href="/A262052/b262052.txt">Table of n, a(n) for n = 1..10000</a> (term 1..65 from Daniel Lignon)
%t A262052 eulerPseudoQ[n_?PrimeQ, b_] = False; eulerPseudoQ[n_, b_] := Block[{p = PowerMod[b, (n - 1)/2, n]}, p == Mod[1, n] || p == Mod[-1, n]]; Select[2 Range[27000] + 1, eulerPseudoQ[#, 5] &] (* _Michael De Vlieger_, Sep 09 2015, after _Jean-François Alcover_ at A006970 *)
%o A262052 (PARI) for(n=1, 1e5, if( Mod(5, (2*n+1))^n == 1 || Mod(5, (2*n+1))^n == 2*n && bigomega(2*n+1) != 1 , print1(2*n+1", "))); \\ _Altug Alkan_, Oct 11 2015
%Y A262052 Cf. A006970 (base 2), A262051 (base 3), this sequence (base 5), A262053 (base 6), A262054 (base 7), A262055 (base 8).
%K A262052 nonn
%O A262052 1,1
%A A262052 _Daniel Lignon_, Sep 09 2015