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 A066719 #25 Apr 13 2025 07:56:51
%S A066719 1,2,4,6,96
%N A066719 Numbers k such that 1 + k^phi(k) is prime.
%C A066719 _Robert G. Wilson v_ reports no more primes up to 1400. - _N. J. A. Sloane_, Sep 22 2004
%C A066719 Any additional terms are larger than 6000. - _Rick L. Shepherd_, Apr 03 2002
%C A066719 Further terms are greater than 10000. - _Charles R Greathouse IV_, Nov 23 2010
%C A066719 a(6) > 60000. - _Michael S. Branicky_, Apr 13 2025
%e A066719 4^phi(4) + 1 = 4^2 + 1 = 17, a prime, so 4 is a term of the sequence.
%t A066719 Do[s=1+n^(EulerPhi[n]); If[PrimeQ[s], Print[{n, s}]], {n, 1, 1000}]
%o A066719 (PARI) for(n=1,6000,print(n); s=1+n^eulerphi(n); if(isprime(s),print(n," ",s)))
%o A066719 /* It suffices to search only even n - with, e.g., PARI forstep (n=6002,7000,2,...) - because a(1)=1 is the only possible odd term. (Note that the average number of digits of s ( length(Str(s)) ) for the 500 even candidates from 6002 to 7000 is 10048 with a minimum of 5087 digits and a maximum of 13450 digits). */
%o A066719 \\ _Rick L. Shepherd_, Apr 03 2002
%Y A066719 Cf. A067975, A000010.
%K A066719 nonn,hard,more
%O A066719 1,2
%A A066719 _Joseph L. Pe_, Jan 14 2002
%E A066719 Edited by _T. D. Noe_, Oct 30 2008