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 A045646 #15 Mar 08 2020 22:57:53
%S A045646 1,10,19,199,19999999999999999999999
%N A045646 Alternative version of A006050.
%C A045646 This is also the smallest n such that digit sum of n = previous term. - _Dominick Cancilla_, Aug 09 2010
%D A045646 H. J. Hindin, The additive persistence of a number, J. Rec. Math., 7 (No. 2, 1974), 134-135.
%H A045646 N. J. A. Sloane, <a href="http://neilsloane.com/doc/persistence.html">The persistence of a number</a>, J. Recreational Math., 6 (1973), 97-98.
%F A045646 For n > 1, a(n) = 2*10^((a(n-1)-1)/9) - 1.
%t A045646 Join[{1},NestList[2*10^((#-1)/9)-1&,10,3]] (* _Harvey P. Dale_, Sep 20 2011 *)
%Y A045646 Cf. A003001, A006050.
%K A045646 nonn,base,nice
%O A045646 0,2
%A A045646 _N. J. A. Sloane_
%E A045646 Next term is 1 followed by 2222222222222222222222 9s.