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 A083734 #19 Jun 29 2019 08:32:41 %S A083734 1541,1729,1891,2821,6601,8911,15841,29341,41041,46657,52633,63973, %T A083734 75361,88831,101101,112141,115921,126217,146611,162401,172081,188461, %U A083734 218791,252601,294409,314821,334153,340561,342271,399001,410041,416641 %N A083734 Pseudoprimes to bases 3 and 5. %H A083734 Amiram Eldar, <a href="/A083734/b083734.txt">Table of n, a(n) for n = 1..15806</a> (terms 1..147 from R. J. Mathar) %H A083734 F. Richman, <a href="http://math.fau.edu/Richman/carm.htm">Primality testing with Fermat's little theorem</a> %F A083734 a(n) = n-th positive integer k(>1) such that 3^(k-1) = 1 (mod k) and 5^(k-1) = 1 (mod k). %e A083734 a(1)=1541 since it is the first nonprime number such that 3^(k-1) = 1 (mod k) and 5^(k-1) = 1 (mod k). - clarified by _Harvey P. Dale_, Jan 29 2013 %t A083734 Select[Range[420000],!PrimeQ[#]&&PowerMod[3,#-1,#]==PowerMod[5,#-1,#]==1&] (* _Harvey P. Dale_, Jan 29 2013 *) %Y A083734 Intersection of A005935 and A005936. %K A083734 easy,nonn %O A083734 1,1 %A A083734 Serhat Sevki Dincer (sevki(AT)ug.bilkent.edu.tr), May 05 2003