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 A074920 #8 May 10 2019 16:01:58
%S A074920 1,2,3,4,33,39,99,3237,9711,2069301,6207903,45502509,24091595067
%N A074920 Integers k such that phi(k) = 6k/Pi^2 rounded to nearest integer.
%C A074920 The average value of phi(n) can be approximated for large n by 6n/Pi^2 (Tattersall, p. 162).
%D A074920 James J. Tattersall, "Elementary Number Theory in Nine Chapters", Cambridge University Press, 2001.
%e A074920 phi(99) = 60 and 6*99/Pi^2 = 60.1848...., which rounds off to 60. Hence 99 is a term of the sequence.
%t A074920 s = Pi^2; l = {}; Do[ If[Abs[EulerPhi[n] - 6 n/ s] <= 0.5, l = Append[l, n]], {n, 1, 10^5}]; l
%Y A074920 Cf. A000010, A072355.
%Y A074920 Cf. A059956 (6/Pi^2).
%K A074920 nonn,more
%O A074920 1,2
%A A074920 _Joseph L. Pe_, Oct 01 2002
%E A074920 a(10)-a(13) from _Amiram Eldar_, May 10 2019
%E A074920 Name edited by _Michel Marcus_, May 10 2019