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 A212818 #18 Feb 16 2025 08:33:17
%S A212818 1,5,49,493,4953,49856,499735,4999579,49998058,499987392,4999941987,
%T A212818 49999828888,499999738687,4999999516711
%N A212818 Numbers up to 10^n with an even number of not necessarily distinct prime factors, or positive Liouville function.
%H A212818 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/LiouvilleFunction.html">Liouville Function</a>
%F A212818 a(n) = A011557(n) - A212819(n).
%F A212818 a(n) = (10^n)/2 + A090410(n)/2. - _Donovan Johnson_, May 30 2012
%F A212818 a(n) = A055037(10^n). - _Ray Chandler_, May 30 2012
%e A212818 a(1) = 5 since up to 10 there are the five numbers 1, 4, 6, 9, 10 with an even number of prime factors, or positive Liouville function.
%p A212818 zg:=0: zu:=0: G:=[]: U:=[]: k:=0:
%p A212818 for i from 1 to 10^8 do if numtheory[bigomega](i) mod 2 = 0 then zg:=zg+1: else zu:=zu+1: fi: if i=10^k then G:=[op(G),zg]: U:=[op(U),zu]: k:=k+1: fi: od:
%p A212818 print(G);
%t A212818 Table[Length[Select[Range[10^n], EvenQ[PrimeOmega[#]] &]], {n, 0, 5}] (* _Alonso del Arte_, May 28 2012 *)
%t A212818 Table[Count[LiouvilleLambda[Range[10^n]], 1], {n, 0, 5}] (* _Ray Chandler_, May 30 2012 *)
%Y A212818 Cf. A055037 (goes up to n rather than 10^n), A002819, A008836, A028260, A065043, A090410.
%K A212818 nonn
%O A212818 0,2
%A A212818 _Martin Renner_, May 28 2012
%E A212818 a(9)-a(13) from _Donovan Johnson_, May 30 2012