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 A067143 #19 Apr 17 2023 15:35:27 %S A067143 6,12,18,36,72,90,96,108,162,192,432,486,576,702,768,792,924,1152, %T A067143 1296,1458,2592,2916,3456,3888,4698,5550,6696,7998,8700,10368,10590, %U A067143 11802,12288,16470,17496,18432,33250,39366,52488,56790,79248,124356 %N A067143 Numbers n such that phi(n+1) = 3*phi(n). %H A067143 Donovan Johnson, <a href="/A067143/b067143.txt">Table of n, a(n) for n = 1..1000</a> %t A067143 Position[Partition[EulerPhi[Range[125000]],2,1],_?(#[[2]]==3#[[1]]&), 1,Heads-> False]//Flatten (* _Harvey P. Dale_, Jul 30 2020 *) %o A067143 (PARI) isok(n) = eulerphi(n+1) == 3*eulerphi(n); \\ _Michel Marcus_, Nov 20 2013 %Y A067143 Cf. A001274, A050472, A172314. %K A067143 nonn %O A067143 1,1 %A A067143 _Benoit Cloitre_, Feb 19 2002 %E A067143 More terms from _Dean Hickerson_, Feb 20 2002