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 A248796 #35 Jul 28 2025 09:01:32
%S A248796 3,5,7,17,257,65537,2200696,2619707,6372796,40588487,76466987,
%T A248796 81591196,118018096,206569607,470542487,525644387,726638836,791937616,
%U A248796 971122516,991172807,1268457016,1384822007,1613055047,1709460755,1861556656,1872619667,2507927416,2659263947
%N A248796 Numbers k such that Product_{d|(k-2)} phi(d) = Product_{d|(k-1)} phi(d) where phi(x) = Euler totient function (A000010).
%C A248796 Numbers k such that A029940(k-2) = A029940(k-1).
%C A248796 The first 5 known Fermat primes (A019434) are terms of this sequence.
%F A248796 a(n) = A248795(n) + 2.
%F A248796 A029940(a(n)) = a(n) - 1 if a(n) = prime.
%e A248796 17 is in the sequence because A029940(15) = A029940(16) = 64.
%o A248796 (Magma) [n: n in [3..100000] | (&*[EulerPhi(d): d in Divisors(n-2)]) eq (&*[EulerPhi(d): d in Divisors(n-1)])];
%Y A248796 Supersequence of A247164 and A247203.
%Y A248796 Cf. A000010, A019434, A029940, A248795.
%K A248796 nonn
%O A248796 1,1
%A A248796 _Jaroslav Krizek_, Nov 19 2014
%E A248796 a(7)-a(9) using A248795 by _Jaroslav Krizek_, Nov 19 2014
%E A248796 a(10)-a(20) using A248795 by _Jaroslav Krizek_, Nov 25 2014
%E A248796 More terms from _Jinyuan Wang_, Jul 27 2025