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 A359088 #20 Aug 01 2025 11:35:09 %S A359088 51,111,327,1281,1563 %N A359088 Odd integers k such that the multiplicative order of 2 modulo the largest prime factor of 2^k - 1 is different from k. %C A359088 In other words, odd integers k that are not equal to A002326((A005420(k)-1)/2). %C A359088 Inspired by former comment from _Thomas Ordowski_ in A005420. %o A359088 (PARI) zn(n) = znorder(Mod(2, 2*n+1)); \\ A002326 %o A359088 f(n) = vecmax(factor(2^n-1)[,1]); \\ A005420 %o A359088 isok(k) = (k%2) && (zn((f(k)-1)/2) != k); %Y A359088 Cf. A002326, A005420. %K A359088 nonn,hard,more %O A359088 1,1 %A A359088 _Michel Marcus_, Dec 16 2022 %E A359088 Edited and a(4)-a(5) added by _Max Alekseyev_, Feb 16 2025