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 A254576 #18 Aug 01 2025 19:41:05 %S A254576 3,5,17,257,65537,83623937 %N A254576 Primes p such that phi(p-2) divides p-1 where phi is Euler's totient function (A000010). %C A254576 The first 5 known Fermat primes from A019434 are terms. %C A254576 Conjecture: also primes p such that 2*phi(p-2) = p-1 (i.e., primes in A232720). %C A254576 a(7) > 10^25. - _Max Alekseyev_, Feb 02 2024 %o A254576 (Magma) [n: n in [3..10000000] | IsPrime(n) and (n-1) mod EulerPhi(n-2) eq 0]; %Y A254576 Subsequence of A249541. %Y A254576 Cf. A000010, A019434, A050474, A203966, A232720. %K A254576 nonn,more %O A254576 1,1 %A A254576 _Jaroslav Krizek_, Feb 25 2015