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 A202270 #24 Aug 16 2023 16:14:03
%S A202270 1,20,300,4000,50000,600000,7000000,80000000,900000000,9100000000,
%T A202270 92000000000,930000000000,9400000000000,95000000000000,
%U A202270 960000000000000,9700000000000000,98000000000000000,990000000000000000,9910000000000000000,99200000000000000000
%N A202270 a(n) is the largest n-digit number whose sum of digits is n.
%H A202270 Michael S. Branicky, <a href="/A202270/b202270.txt">Table of n, a(n) for n = 1..1000</a>
%p A202270 a:= n-> (q-> parse(cat([9$q, r, 0$(n-q-1)][])))(iquo(n, 9, 'r')):
%p A202270 seq(a(n), n=1..20); # _Alois P. Heinz_, Aug 16 2023
%o A202270 (PARI) a(n) = my(k=10^n-1); while (sumdigits(k) != n, k--); k; \\ _Michel Marcus_, Aug 16 2023
%o A202270 (Python)
%o A202270 def a(n): return int("9"*(m:=n//9)+str(n%9)+"0"*(n-m-1))
%o A202270 print([a(n) for n in range(1,21)]) # _Michael S. Branicky_, Aug 16 2023
%Y A202270 Cf. A061219 (without zeros).
%Y A202270 Cf. A364578 (smallest n-digit number whose sum of digits is n).
%K A202270 nonn,base
%O A202270 1,2
%A A202270 _Jaroslav Krizek_, Jan 06 2012