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 A348708 #15 Nov 09 2021 06:41:36
%S A348708 0,4,30,303,3053,30421,303857,3039127,30395383,303963673,3039652332,
%T A348708 30396399068,303963519954,3039635209356,30396355530761,
%U A348708 303963552535238,3039635510867921,30396355103617024,303963550950390745,3039635508820145344,30396355092470750098,303963550928711270447
%N A348708 Number of squarefree integers with an odd number of prime factors <= 10^n.
%C A348708 a(n) is the number of integers k <= 10^n with mu(k)=-1 where mu(k) is the Möbius function.
%F A348708 a(n) = (A071172(n) - A084237(n)) / 2.
%F A348708 Lim_{n->oo} a(n)/10^n = 3/Pi^2 (A104141).
%e A348708 a(1) = 4 because there are 4 squarefree integers with an odd number of prime factors <= 10: 2, 3, 5, 7.
%t A348708 Table[Length@Select[Range[10^n],MoebiusMu@#==-1&],{n,0,6}]
%Y A348708 Cf. A071172, A084237, A008683, A030059, A104141, A348709.
%K A348708 nonn
%O A348708 0,2
%A A348708 _Giorgos Kalogeropoulos_, Oct 30 2021