%I #26 Sep 08 2022 08:46:10
%S 3,5,7,17,257,65537,2200696,2619707,6372796,40588487,76466987,
%T 81591196,118018096,206569607,470542487,525644387,726638836,791937616,
%U 971122516,991172807
%N Numbers n such that Product_{d|(n-2)} phi(d) = Product_{d|(n-1)} phi(d) where phi(x) = Euler totient function (A000010).
%C Numbers n such that A029940(n-2) = A029940(n-1).
%C The first 5 known Fermat primes (A019434) are terms of this sequence.
%C Supersequence of A247164 and A247203.
%F a(n) = A248795(n)+2.
%F A029940(a(n)) = a(n)-1 if a(n) = prime.
%e 17 is in the sequence because A029940(15) = A029940(16) = 64.
%o (Magma) [n: n in [3..100000] | (&*[EulerPhi(d): d in Divisors(n-2)]) eq (&*[EulerPhi(d): d in Divisors(n-1)])]
%Y Cf. A000010, A019434, A029940, A247164, A248795.
%K nonn,more
%O 1,1
%A _Jaroslav Krizek_, Nov 19 2014
%E a(7)-a(9) using A248795 by _Jaroslav Krizek_, Nov 19 2014
%E a(10)-a(20) using A248795 by _Jaroslav Krizek_, Nov 25 2014