%I #25 Aug 10 2022 09:57:50
%S 1,0,1,0,1,1,2,1,0,0,1,0,1,1,1,0,1,0,1,0,0,0,1,0,1,1,2,3,2,2,1,2,2,2,
%T 2,3,2,2,2,3,2,2,1,2,3,3,2,3,4,5,5,6,5,6,6,7,7,7,6,7,6,6,7,8,8,8,7,8,
%U 8,8,7,8,7,7,8,9,9,9,8,9,10,10,9,10,10,10,10,11,10,11,11,12,12,12,12,13,12
%N Difference between the number of primes equal to or less than n and (1 + the number of nonsquarefree numbers equal to or less than n).
%H Jinyuan Wang, <a href="/A082926/b082926.txt">Table of n, a(n) for n = 1..10000</a>
%F a(n) = abs(A057627(n) + 1 - A000720(n)). - _Michel Marcus_, Mar 27 2020
%t nsfQ[n_] := n == 1 || ! SquareFreeQ[n]; Abs[Accumulate[Table[If[nsfQ[n], 1, 0] - If[PrimeQ[n], 1, 0], {n, 1, 100}]]] (* _Amiram Eldar_, Jun 13 2022 *)
%o (PARI) a(n) = abs(sum(k=1, n, !issquarefree(k)) + 1 - primepi(n)); \\ _Michel Marcus_, Mar 27 2020
%Y Cf. A000720, A057627.
%K nonn
%O 1,7
%A Anonymous, Apr 15 2003
%E Name edited by _Michel Marcus_, Jun 14 2022