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 A058817 #17 Jan 12 2024 01:26:41
%S A058817 0,2,4,6,8,12,14,16,18,20,22,24,28,30,32,36,38,40,42,44,46,48,54,56,
%T A058817 60,62,64,66,68,70,72,74,76,78,80,82,84,88,90,92,94,96,98,102,104,106,
%U A058817 108,110,112,114,118,120,124,126,128,132,136,138,140,142,144,148,150,152
%N A058817 Even cototient numbers.
%H A058817 Donovan Johnson, <a href="/A058817/b058817.txt">Table of n, a(n) for n = 1..10001</a>
%F A058817 Even terms of A063742.
%e A058817 88 is here because it is the cototient of 120: 88 = 120-phi(120) = 120-32 = 88.
%t A058817 With[{max = 300}, Union@ Select[Table[n - EulerPhi[n], {n, 1, max^2}], # < max && EvenQ[#] &]] (* _Amiram Eldar_, Jan 12 2024 *)
%Y A058817 Cf. A000010, A051953, A063742, A005277, A005278, A002202, A058763.
%K A058817 nonn
%O A058817 1,2
%A A058817 _Labos Elemer_, Jan 04 2001
%E A058817 Offset corrected by _Donovan Johnson_, Nov 17 2013
%E A058817 a(1) = 0 inserted by _Amiram Eldar_, Jan 12 2024