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 A083546 #14 Nov 04 2020 12:39:18
%S A083546 1,2,8,12,48,48,60,80,96,128,144,180,280,240,240,288,288,288,336,288,
%T A083546 384,360,480,480,640,720,672,600,576,720,720,720,672,864,960,864,960,
%U A083546 1080,1008,1408,1296,960,1008,1320,1260,1056,1440,1200,1728,1440,1296
%N A083546 The geometric mean of the Euler totient function of 2 consecutive integers {k, k+1} when it is an integer.
%H A083546 Amiram Eldar, <a href="/A083546/b083546.txt">Table of n, a(n) for n = 1..10000</a>
%F A083546 a(n) = sqrt(A000010(x) * A000010(x+1)) = sqrt(phi(x) * phi(x+1)) = sqrt(A083542(x)) where x = A083545(n).
%e A083546 12 is a term since sqrt(phi(19) * phi(20)) = sqrt(18 * 8) = sqrt(144) = 12.
%t A083546 f[x_] := EulerPhi[x]; Do[s=Sqrt[f[n+1]*f[n]]; If[IntegerQ[s], Print[s]], {n, 1, 5000}]
%t A083546 Select[Sqrt[#]&/@(Times@@@Partition[EulerPhi[Range[3000]],2,1]),IntegerQ] (* _Harvey P. Dale_, Nov 04 2020 *)
%Y A083546 Cf. A000010, A083542, A083542, A066813, A058515, A083542, A083545.
%K A083546 nonn
%O A083546 1,2
%A A083546 _Labos Elemer_, May 21 2003