|
%I #12 Sep 08 2022 08:45:06
%S 0,0,1,1,2,1,3,2,3,2,4,2,5,3,4,4,6,3,7,4,5,4,8,4,8,5,7,5,9,4,10,6,8,6,
%T 9,5,11,7,9,6,12,5,13,8,9,8,14,6,13,8,11,9,15,7,12,9,11,9,16,6,17,10,
%U 11,11,15,8,18,11,14,9,19,9,20,11,12,11,17,9,21,11,16,12,22,9,18,13,16
%N Number of primes not exceeding phi(n).
%H Vincenzo Librandi, <a href="/A070804/b070804.txt">Table of n, a(n) for n = 1..2000</a>
%F a(n) = A000720(A000010(n)) = pi(phi(n)).
%e n=50: phi[50]=20,Pi[20]=8=a(50)
%t Table[PrimePi[EulerPhi[n]], {n, 1, 256}]
%o (Magma) [#PrimesUpTo(EulerPhi(n)): n in [1..90]]; // _Vincenzo Librandi_, Mar 26 2017
%Y Cf. A007818, A000010, A000720, A070800, A070801, A070802, A070803.
%K easy,nonn
%O 1,5
%A _Labos Elemer_, May 08 2002
|
