A070804 Number of primes not exceeding phi(n).
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, 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, 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
Offset: 1
Examples
n=50: phi[50]=20,Pi[20]=8=a(50)
Links
- Vincenzo Librandi, Table of n, a(n) for n = 1..2000
Programs
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Magma
[#PrimesUpTo(EulerPhi(n)): n in [1..90]]; // Vincenzo Librandi, Mar 26 2017
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Mathematica
Table[PrimePi[EulerPhi[n]], {n, 1, 256}]