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 A066813 #22 May 07 2025 03:04:10
%S A066813 1,2,2,4,4,6,12,12,12,20,20,12,12,24,8,16,48,18,72,24,60,110,88,40,60,
%T A066813 36,36,84,56,120,240,80,80,48,24,36,36,72,48,80,120,84,420,120,264,
%U A066813 506,368,336,420,160,96,312,468,360,120,72,252,812,464,240,60,180,288,96
%N A066813 a(n) = lcm(phi(n), phi(n+1)).
%H A066813 Harry J. Smith, <a href="/A066813/b066813.txt">Table of n, a(n) for n = 1..1000</a>
%F A066813 a(n) = A083542(n)/A058515(n). - _Amiram Eldar_, May 07 2025
%t A066813 LCM@@EulerPhi[#]&/@Partition[Range[100],2,1] (* _Harvey P. Dale_, May 07 2011 *)
%o A066813 (PARI) a(n) = { lcm(eulerphi(n), eulerphi(n+1)) } \\ _Harry J. Smith_, Mar 29 2010
%Y A066813 Cf. A000010 (phi), A058515, A083542.
%K A066813 nonn,easy
%O A066813 1,2
%A A066813 _Benoit Cloitre_, Jan 20 2002