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 A275159 #18 Aug 04 2025 20:24:51 %S A275159 2,3,5,17,257,65537,548898078721,1151122703583805441, %T A275159 77370970260794891965562881,632834090662785970268956262401, %U A275159 1327149278901642923121482163604684801,2787593149816327845958662202634335514787841,91343852333181430856373443055921906148567941121 %N A275159 Primes p such that p-1 is the value of totient function of a product of distinct Fermat numbers (A000215). %C A275159 Primes p such that p-1 = phi(A001317(x)) has solution. %e A275159 Prime 548898078721 is in the sequence because 548898078720 = phi(1095216660735) = phi(3*5*17*4294967297); all numbers 3, 5, 17 and 4294967297 are terms of A000215 (Fermat numbers). %o A275159 (Magma) Set(Sort([EulerPhi(k)+1: k in [A001317(n)] | IsPrime(EulerPhi(k)+1)])); %Y A275159 Supersequence of A019434 (Fermat primes) and A092506 (primes of the form 2^n+1). %Y A275159 Cf. A000010, A000215, A001317, A019434, A092506. %K A275159 nonn %O A275159 1,1 %A A275159 _Jaroslav Krizek_, Nov 13 2016 %E A275159 a(13) from _Jinyuan Wang_, Nov 01 2020