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 A354870 #14 Dec 07 2023 21:37:51
%S A354870 1,1,1,1,1,2,1,1,1,2,1,2,1,2,2,1,1,2,1,2,2,2,1,2,1,2,1,2,1,5,1,1,2,2,
%T A354870 2,2,1,2,2,2,1,5,1,2,2,2,1,2,1,2,2,2,1,2,2,2,2,2,1,5,1,2,2,1,2,5,1,2,
%U A354870 2,5,1,2,1,2,2,2,2,5,1,2,1,2,1,5,2,2,2,2,1,5,2,2,2,2,2,2,1,2,2,2,1,5,1,2,5
%N A354870 Number of nonprime squarefree divisors of n.
%C A354870 Number of terms of A000469 that divide n.
%H A354870 Antti Karttunen, <a href="/A354870/b354870.txt">Table of n, a(n) for n = 1..65537</a>
%H A354870 <a href="/index/Eu#epf">Index entries for sequences computed from exponents in factorization of n</a>
%F A354870 a(n) = Sum_{d|n} A354819(d).
%F A354870 For all n >= 1, a(n) = a(A046523(n)).
%F A354870 a(n) = A034444(n) - A001221(n). - _Ridouane Oudra_, Dec 07 2023
%p A354870 with(numtheory): seq(2^nops(factorset(n)) - nops(factorset(n)), n=1..80); # _Ridouane Oudra_, Dec 07 2023
%t A354870 a[n_] := DivisorSum[n, 1 &, ! PrimeQ[#] && SquareFreeQ[#] &]; Array[a, 100] (* _Amiram Eldar_, Jun 11 2022 *)
%o A354870 (PARI)
%o A354870 A354819(n) = ((1!=bigomega(n))&&issquarefree(n));
%o A354870 A354870(n) = sumdiv(n,d,A354819(d));
%Y A354870 Inverse Möbius transform of A354819.
%Y A354870 Cf. A000469, A046523.
%Y A354870 Differs from A259936 for the first time at n=210, where a(210) = 12, while A259936(210) = 15.
%Y A354870 Cf. A034444, A001221.
%K A354870 nonn
%O A354870 1,6
%A A354870 _Antti Karttunen_, Jun 11 2022