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 A294903 #11 Jul 20 2023 07:01:24
%S A294903 1,2,2,2,2,3,2,2,2,3,2,3,2,3,3,2,2,3,2,3,3,3,2,3,3,3,2,3,2,4,2,2,3,3,
%T A294903 3,3,2,3,3,3,2,4,2,3,3,3,2,3,2,4,3,3,2,3,3,3,3,3,2,4,2,3,3,2,3,4,2,3,
%U A294903 3,4,2,3,2,3,4,3,3,4,2,3,2,3,2,4,3,3,3,3,2,4,3,3,3,3,4,3,2,3,3,4,2,4,2,3,4,3,2,3,2,4,4,3,2,4,3,3,3,3,4,4
%N A294903 Number of divisors of n that are in A257691.
%C A294903 Number of terms of A257691 that divide n.
%H A294903 Antti Karttunen, <a href="/A294903/b294903.txt">Table of n, a(n) for n = 1..25000</a>
%F A294903 a(n) = Sum_{d|n} A294905(d).
%F A294903 a(n) = A294901(n) + A294905(n).
%F A294903 a(n) + A294904(n) = A000005(n).
%t A294903 q[n_] := DivisorSum[n, DigitCount[#, 2, 1] &] <= 2*DigitCount[n, 2, 1]; a[n_] := DivisorSum[n, 1 &, q[#] &]; Array[a, 100] (* _Amiram Eldar_, Jul 20 2023 *)
%o A294903 (PARI)
%o A294903 A292257(n) = sumdiv(n,d,(d<n)*hammingweight(d));
%o A294903 A294905(n) = (A292257(n) <= hammingweight(n));
%o A294903 A294903(n) = sumdiv(n,d,A294905(d));
%Y A294903 Cf. A000120, A257691, A292257, A294901, A294902, A294904, A294905.
%Y A294903 Cf. also A294893.
%K A294903 nonn,base
%O A294903 1,2
%A A294903 _Antti Karttunen_, Nov 10 2017