A362334 a(n) = A000010(n) + A000010(n+2), where A000010 is the Euler phi-function.

3, 3, 6, 4, 10, 6, 12, 8, 16, 8, 22, 10, 20, 14, 24, 14, 34, 14, 30, 18, 34, 18, 42, 20, 38, 24, 46, 20, 58, 24, 50, 32, 44, 28, 60, 30, 60, 34, 64, 28, 82, 32, 66, 42, 70, 38, 88, 36, 74, 44, 84, 42, 92, 42, 76, 52, 94, 44, 118, 46, 96, 62, 84, 52, 114, 52, 110

Offset: 1

Author

Alexandre Herrera, Apr 16 2023

Keywords

• nonn

Comments

Conjecture: a(2*n) <= a(2*n-1) and a(2*n) < a(2*n+1).

Examples

			For n = 3, phi(3) = 2 and phi(5) = 4, so a(3) = 6.
		

Crossrefs

Cf. A000010, A092404.

Programs

Mathematica

a[n_] := Plus @@ EulerPhi[n + {0, 2}]; Array[a, 100] (* Amiram Eldar, Apr 18 2023 *)

PARI

a(n) = eulerphi(n) + eulerphi(n+2); \\ Michel Marcus, Apr 17 2023

Formula

a(n) = phi(n) + phi(n+2).