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 A382968 #7 Apr 11 2025 08:16:10
%S A382968 1,1,1,1,1,1,1,1,1,1,2,1,1,1,1,1,1,1,1,1,1,1,2,1,1,1,1,1,1,1,1,2,1,2,
%T A382968 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,2,1,1,1,2,1,2,1,1,1,2,
%U A382968 1,2,1,1,1,1,1,1,1,1,1,2,1,1,1,1,1,1,1
%N A382968 The number of non-unitary prime divisors of the n-th biquadratefree number that is not squarefree.
%H A382968 Amiram Eldar, <a href="/A382968/b382968.txt">Table of n, a(n) for n = 1..10000</a>
%F A382968 a(n) = A056170(A382967(n)).
%F A382968 Asymptotic mean: Limit_{m->oo} (1/m) * Sum_{k=1..m} a(k) = (15/(15-Pi^2)) * Sum_{p prime} (1/(p^2+1)) = 1.13751331982931014416... .
%t A382968 f[k_] := If[k == 1, Nothing, Module[{e = FactorInteger[k][[;; , 2]]}, If[2 <= Max[e] <= 3, Count[e, _?(# > 1 &)], Nothing]]]; Array[f, 1000]
%o A382968 (PARI) list(lim) = {my(e, emax); for(k = 2, lim, e = factor(k)[, 2]; emax = vecmax(e); if(emax > 1 && emax < 4, print1(#select(x -> x > 1, e), ", ")));}
%Y A382968 Cf. A056170, A382425, A382965, A382966, A382967.
%K A382968 nonn,easy
%O A382968 1,11
%A A382968 _Amiram Eldar_, Apr 10 2025