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 A209928 #32 Feb 21 2025 11:26:57
%S A209928 1,2,3,4,5,6,7,8,9,5,1,6,3,7,5,8,7,9,9,5,7,2,3,8,5,6,9,8,9,6,3,8,3,7,
%T A209928 7,9,7,9,9,8,4,7,4,4,9,6,7,8,9,5,7,6,5,9,5,8,9,9,9,6,6,6,9,8,6,6,7,8,
%U A209928 9,7,7,9,7,7,7,9,7,9,9,8,9,8,8,8,8,8,9
%N A209928 Largest digit of all divisors of n.
%C A209928 Also largest digit of concatenation of all divisors of n (A037278, A176558).
%C A209928 a(n) = 9 for almost all n. - _Charles R Greathouse IV_, Mar 20 2012
%C A209928 With an offset of 1 rather than 0, A016186 tells us how many integers among the first 10^n have 9s among their digits, and those numbers are therefore guaranteed to index a 9 in this sequence. More interesting of course are those numbers that don't have a 9 in their own digits but do have a 9 among the digits of their nontrivial divisors. - _Alonso del Arte_, Mar 23 2012
%H A209928 Michael S. Branicky, <a href="/A209928/b209928.txt">Table of n, a(n) for n = 1..10000</a>
%e A209928 a(12) = 6 because digit 6 is largest digit of all divisors of 12: (1, 2, 3, 4, 6, 12).
%t A209928 Flatten[Table[Take[Sort[Flatten[IntegerDigits[Divisors[n]]]], -1], {n, 100}]] (* _Alonso del Arte_, Mar 23 2012 *)
%o A209928 (PARI) a(n)=my(t);fordiv(n, d, t=max(t, vecmax(eval(Vec(Str(d))))); if(t>8, return(t)));t \\_Charles R Greathouse IV_, Mar 20 2012
%o A209928 (Python)
%o A209928 from sympy import divisors
%o A209928 def a(n): return int(max("".join(map(str, divisors(n)))))
%o A209928 print([a(n) for n in range(1, 88)]) # _Michael S. Branicky_, Feb 22 2021
%Y A209928 Cf. A054055 (largest digit of n).
%K A209928 nonn,base
%O A209928 1,2
%A A209928 _Jaroslav Krizek_, Mar 20 2012