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 A231817 #12 Jul 30 2019 12:22:26
%S A231817 1,2,3,8,5,8,7,8,4,0,1,6,3,0,5,0,7,0,9,0,8,8,6,8,0,4,6,0,8,0,3,0,4,6,
%T A231817 0,0,2,8,8,0,4,0,2,0,0,6,6,0,0,0,0,0,5,0,0,0,0,0,0,0,6,4,0,0,0,0,8,0,
%U A231817 2,0,7,0,2,8,0,0,8,0,8,0,0,6,8,0,0,0,0
%N A231817 Multiplicative digital root of concatenation of all divisors of n (A037278).
%C A231817 Also multiplicative digital root of A190997 (product of digits of all the divisors of n) or A007955 (product of divisors of n).
%C A231817 Conjecture: a(n) = 0 for almost all n.
%C A231817 793 of the first 1000 terms are zeros, and 9147 out of the first 10000 terms are zeros. - _Harvey P. Dale_, Jul 30 2019
%H A231817 Harvey P. Dale, <a href="/A231817/b231817.txt">Table of n, a(n) for n = 1..1000</a>
%e A231817 For n=12: 1*2*3*4*6*1*2=288, 2*8*8=128, 1*2*8=16, 1*6=6; a(12)=6.
%t A231817 Table[NestWhile[Times@@IntegerDigits[#]&,Times@@Flatten[ IntegerDigits/@ Divisors[ n]], #>9&],{n,90}] (* _Harvey P. Dale_, Jul 30 2019 *)
%Y A231817 Cf. A037278, A007955, A190998 (associative digital root of digits of all the divisors of n), A031347 (multiplicative digital root of n).
%K A231817 nonn,base
%O A231817 1,2
%A A231817 _Jaroslav Krizek_, Nov 13 2013