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 A279913 #25 Jul 25 2022 04:03:00
%S A279913 1,92,993,9994,99995,999996,9999997,99999998,999999999,9999999910,
%T A279913 99999999911,999999999912,9999999999913,99999999999914,
%U A279913 999999999999915,9999999999999916,99999999999999917,999999999999999918,9999999999999999919,99999999999999999920
%N A279913 Largest n-digit number ending in n.
%F A279913 a(n) = n + 10^n - 10^(1 + floor(log_10(n))). - _Wesley Ivan Hurt_, Mar 30 2020
%F A279913 a(n) = 10^n - A089186(n). - _Michel Marcus_, Jul 25 2022
%t A279913 Table[n + 10^n - 10^(1 + Floor[Log10[n]]), {n, 100}] (* _Wesley Ivan Hurt_, Mar 30 2020 *)
%o A279913 (Python)
%o A279913 def A279913(n): return 10**n+n-10**(len(str(n))) # _Chai Wah Wu_, Jul 25 2022
%o A279913 (PARI) a(n) = 10^n + n - 10^(#Str(n)); \\ _Michel Marcus_, Jul 25 2022
%Y A279913 Cf. A266959.
%Y A279913 Cf. A011557 (10^n), A089186.
%K A279913 nonn,base
%O A279913 1,2
%A A279913 _Wesley Ivan Hurt_, Dec 22 2016