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 A306144 #33 Sep 15 2018 16:09:11 %S A306144 286,16531,24046,49051,72041,182527,192713,232726,258017,327781, %T A306144 442471,443713,453259,574397,625873,652879,655051,668431,705091, %U A306144 903631,1236031,1241143,1250833,1287091,1304446,1309111,1351601,1414639,1563151,1817743,1899451,1908397 %N A306144 Numbers k > 2 such that 3^(k-1) == 1 (mod k) and gcd(k, 2^(k-1)-1) = 1. %C A306144 The odd terms are "anti-Carmichael pseudoprimes (3,2)" defined as follows: numbers k > 1 such that 3^k == 3 (mod k) and gcd(k, 2^k-2) = 1. Cf. A300762 (2,3). %C A306144 We impose k>2, since we want these to be pseudoprimes, thus composite numbers. %t A306144 Select[Range[3, 2*10^6], PowerMod[3, #-1, #] == 1 && GCD[#, #-1 + PowerMod[2, #-1, #]] == 1 &] (* _Giovanni Resta_, Aug 18 2018 *) %o A306144 (PARI) isok(k) = (k>2) && (Mod(3, k)^(k-1) == Mod(1, k)) && (gcd(k, 2^(k-1)-1) == 1); \\ _Michel Marcus_, Aug 18 2018 %Y A306144 Subsequence of A005935. %Y A306144 Cf. A130433. %K A306144 nonn %O A306144 1,1 %A A306144 _Thomas Ordowski_, Aug 18 2018 %E A306144 More terms from _Michel Marcus_, Aug 18 2018 %E A306144 Further terms from _Giovanni Resta_, Aug 18 2018