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 A328230 #20 Sep 08 2022 08:46:24 %S A328230 1,2,4,5,14,244,365,434,854,2294,3794,5966,7874,10877,26474,33914, %T A328230 117614,188774,231434,284354,487634,501038,589154,593774,621674, %U A328230 755594,1255814,1306934,1642094,1911194,2193124,2434754,2484674,2507834,2621654,2643494,3512114,3759854,3997574,4082246 %N A328230 Numbers m that divide 3^(m + 1) + 1. %C A328230 Conjecture: For k > 2, k^(m + 1) == -1 (mod m) has an infinite number of positive solutions. %H A328230 Chai Wah Wu, <a href="/A328230/b328230.txt">Table of n, a(n) for n = 1..1528</a> (n = 1..100 from Robert Israel) %p A328230 filter:= m -> 3 &^ (m+1) + 1 mod m = 0: %p A328230 select(filter, [$1..10^7]); # _Robert Israel_, Oct 30 2019 %o A328230 (Magma) [n+1: n in [0..5000000] | Modexp(3,n+2,n+1) eq n]; %o A328230 (PARI) isok(m) = Mod(3, m)^(m+1) == -1; \\ _Michel Marcus_, Oct 10 2019 %Y A328230 Cf. A055685, A277289, A296369. %K A328230 nonn %O A328230 1,2 %A A328230 _Juri-Stepan Gerasimov_, Oct 08 2019