A008331 a(n) = phi(prime(n)+1).

2, 2, 2, 4, 4, 6, 6, 8, 8, 8, 16, 18, 12, 20, 16, 18, 16, 30, 32, 24, 36, 32, 24, 24, 42, 32, 48, 36, 40, 36, 64, 40, 44, 48, 40, 72, 78, 80, 48, 56, 48, 72, 64, 96, 60, 80, 104, 96, 72, 88, 72, 64, 110, 72, 84, 80, 72, 128, 138, 92, 140, 84, 120, 96, 156, 104, 164, 156, 112, 120, 116

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn

Links

• Michael De Vlieger, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000010, A008864, A363700.

Programs

Maple

for i from 1 to 500 do if isprime(i) then print(phi(i+1)); fi; od;

Mathematica

EulerPhi[1 + Prime@ Range@ 71] (* Michael De Vlieger, Feb 17 2021 *)

PARI

a(n) = eulerphi(prime(n)+1); \\ Michel Marcus, Feb 17 2021

Formula

a(n) = A000010(A008864(n)). - Michel Marcus, Feb 17 2021

Extensions

Offset 1 from Michel Marcus, Feb 17 2021