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 A363583 #28 Sep 12 2023 15:51:08 %S A363583 1,3,5,7,11,13,15,23,33,35,37,43,47,53,61,67,69,71,77,87,95,103,113, %T A363583 119,123,127,133,137,143,159,163,167,177,181,191,193,209,211,217,249, %U A363583 251,257,259,263,267,271,277,293,299,307,313,329,331,335,337,339 %N A363583 Numbers k such that 2*phi(k)+k is a prime, where phi is A000010. %C A363583 All the terms are odd squarefree numbers. %t A363583 Select[Range[1, 350, 2], PrimeQ[2*EulerPhi[#] + #] &] (* _Amiram Eldar_, Aug 17 2023 *) %o A363583 (Python) %o A363583 from sympy import totient, isprime %o A363583 print([k for k in range(1, 340) if isprime(2*totient(k) + k)]) %o A363583 (PARI) isok(k) = isprime(k+2*eulerphi(k)); \\ _Michel Marcus_, Aug 20 2023 %Y A363583 Cf. A000010, A068080. %Y A363583 Subsequence of A056911. %Y A363583 Subsequence: A088878 (the prime terms). %K A363583 nonn,easy %O A363583 1,2 %A A363583 _Darío Clavijo_, Aug 17 2023