The OEIS is supported by the many generous donors to the OEIS Foundation.
%I #8 Oct 14 2021 15:48:10
%S 1,2,3,4,5,6,7,8,9,10,10,11,12,13,14,15,16,17,18,19,20,20,20,21,21,22,
%T 23,24,24,25,25,26,26,27,28,29,30,31,32,33,33,34,34,34,35,35,35,36,36,
%U 36,37,38,38,39,39,40,41,41,41,42,42,42,43,44,45,45,45,46,46,47,47,48
%N Number of numbers <= n with 3-smooth Euler's totient (A000010).
%C Partial sums of A122255.
%t b[n_] := Boole[FactorInteger[EulerPhi[n]][[-1, 1]] <= 3];
%t Table[b[n], {n, 1, 100}] // Accumulate (* _Jean-François Alcover_, Oct 14 2021 *)
%Y Cf. A000010, A071521, A122255.
%K nonn
%O 1,2
%A _Reinhard Zumkeller_, Aug 29 2006