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 A006050 M4683 #34 Mar 10 2025 11:50:50
%S A006050 0,10,19,199,19999999999999999999999
%N A006050 Smallest number of additive persistence n.
%C A006050 The next term a(5) is 1 followed by 2222222222222222222222 9's.
%D A006050 Meimaris Antonios, On the additive persistence of a number in base p, Preprint, 2015.
%D A006050 H. J. Hindin, The additive persistence of a number, J. Rec. Math., 7 (No. 2, 1974), 134-135.
%D A006050 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H A006050 Shyam Sunder Gupta, <a href="https://doi.org/10.1007/978-981-97-2465-9_1">Digital Root Wonders</a>, Exploring the Beauty of Fascinating Numbers, Springer (2025) Ch. 1, 1-28.
%H A006050 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.
%H A006050 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/AdditivePersistence.html">Additive Persistence.</a>
%F A006050 For n>1 a(n) = 2*10^((a(n-1)-1)/9)-1.
%t A006050 lst = {0, 10}; Do[AppendTo[lst, 2*10^((lst[[-1]] - 1)/9) - 1], {3}]; lst (* _Arkadiusz Wesolowski_, Oct 17 2012 *)
%t A006050 Join[{0},NestList[2*10^((#-1)/9)-1&,10,3]] (* _Harvey P. Dale_, May 08 2020 *)
%Y A006050 Cf. A003001, A031286, A045646.
%K A006050 nonn,base,nice
%O A006050 0,2
%A A006050 _N. J. A. Sloane_