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 A333316 #9 Mar 15 2020 07:25:26 %S A333316 216,660,1484,1560,8208,52164,544320,592956,649800,4321800,5103210, %T A333316 6182220,10621380,21415680,24471720,135307008,359624088,535019100, %U A333316 1071782250,1113233520,1227427740,1527496740,9462748008,143935711920 %N A333316 Numbers k such that k^2 + 1 is a Fermat pseudoprime to base 3. %C A333316 a(24) > 7*10^10. %C A333316 The corresponding pseudoprimes a(n)^2 + 1 are 46657, 435601, 2202257, 2433601, 67371265, ... %C A333316 a(25) > 7.5*10^11. - _Giovanni Resta_, Mar 15 2020 %e A333316 216 is a term since 216^2 + 1 = 46657 is a Fermat pseudoprime to base 3. %t A333316 Select[Range[10^3], CompositeQ[#^2 + 1] && PowerMod[3, #^2, #^2 + 1] == 1 &] %Y A333316 Cf. A002522, A005574, A005935, A135590. %K A333316 nonn,more %O A333316 1,1 %A A333316 _Amiram Eldar_, Mar 14 2020 %E A333316 a(24) from _Giovanni Resta_, Mar 15 2020