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 A039789 #15 Jun 10 2025 03:27:13
%S A039789 7,15,62,65,76,98,260,980
%N A039789 Integers k such that phi(k) is equal to the product of (the sum of prime factors and the sum of exponents) of k+1.
%C A039789 Next term if it exists is greater than 1500000. - _Reiner Martin_, May 20 2001
%C A039789 No further terms up to 20000000. - _Harvey P. Dale_, Apr 19 2013
%C A039789 a(9) > 10^10, if it exists. - _Amiram Eldar_, Jun 10 2025
%e A039789 62 is a term since phi(62) = 30, 63 = 3^2*7^1, (3+7)*(2+1) = 30.
%t A039789 epQ[n_]:=Module[{fi=Transpose[FactorInteger[n+1]]},EulerPhi[n]== Total[ First[fi]]* Total[Last[fi]]]; Select[Range[1000],epQ] (* _Harvey P. Dale_, Apr 19 2013 *)
%o A039789 (PARI) isok(k) = my(f=factor(k+1)); eulerphi(k) == vecsum(f[,1]) * vecsum(f[,2]); \\ _Michel Marcus_, Oct 30 2022
%Y A039789 Cf. A000010, A039697, A039774, A039788.
%K A039789 nonn,more
%O A039789 1,1
%A A039789 _Olivier Gérard_