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 A387463 #15 Aug 30 2025 15:56:52
%S A387463 0,0,1,0,0,1,0,0,1,0,0,1,1,0,1,0,0,1,0,0,1,0,1,1,0,1,1,0,0,2,1,1,3,1,
%T A387463 1,2,1,1,3,0,0,1,1,0,1,1,0,1,0,0,1,1,1,1,0,0,1,0,0,2,0,1,2,1,1,3,0,1,
%U A387463 2,1,0,2,1,1,1,1,0,3,0,0,1,0,1,1,0,1,1,0,0,2,1,1,3,0,0,2,0,0,3
%N A387463 Total number of 3's in the decimal digits of the divisors of n.
%H A387463 Robert Israel, <a href="/A387463/b387463.txt">Table of n, a(n) for n = 1..10000</a>
%e A387463 a(33) = 3 because among the divisors of 33, 3 has one 3 and 33 has two, for a total of 3.
%p A387463 f:= proc(n) local t; add(subs(x=1, t)^3, t = expand((1+x+x^2)^n)) end proc:
%p A387463 map(f, [$1..100]);
%t A387463 a[n_]:=Count[Flatten[IntegerDigits/@Divisors[n]],3];Array[a,99] (* _James C. McMahon_, Aug 30 2025 *)
%o A387463 (Python)
%o A387463 from sympy import divisors
%o A387463 def a(n): return sum(str(d).count("3") for d in divisors(n, generator=True))
%o A387463 print([a(n) for n in range(1, 100)]) # _Michael S. Branicky_, Aug 29 2025
%Y A387463 Cf. A385494, A387394, A387464.
%K A387463 nonn,new
%O A387463 1,30
%A A387463 _Robert Israel_, Aug 29 2025