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 A063830 #16 May 01 2019 05:39:45
%S A063830 1,3,9,21,45,117,297,585,1521,3105,6993,14553,43653,90885,185925,
%T A063830 397125,847125,1813125,3238725,7556829,17253789,36910365,94571997,
%U A063830 220301277,475043037,47979336637,183450404605,525019294077
%N A063830 a(n+1) is the smallest odd m whose cototient equals a(n).
%F A063830 a(n) = Min{x, odd : A051953[ a(n-1) ]=a(n)}; a(1)=1; a(2)=3, least odd prime; a(n) = Min[ Select[ Range[ a, b ], Equal[ #-EulerPhi[ # ], a(n-1) ]& ] ].
%e A063830 a(5)=45, cototient(45) = 45 - Phi(45) = 45 - 24 = 21 = a(4). This iteration with even numbers might stop, like {1,2,4,6,10} does if the last computed number has no inverse cototient, like 10 which is a non-cototient number.
%Y A063830 Cf. A005278, A051953.
%K A063830 nonn
%O A063830 1,2
%A A063830 _Labos Elemer_, Aug 21 2001
%E A063830 More terms from _David Wasserman_, Jul 23 2002
%E A063830 a(26)-a(28) from _Donovan Johnson_, Feb 06 2010