A121048 a(n) = n + phi(n), where phi is the Euler totient function.

2, 3, 5, 6, 9, 8, 13, 12, 15, 14, 21, 16, 25, 20, 23, 24, 33, 24, 37, 28, 33, 32, 45, 32, 45, 38, 45, 40, 57, 38, 61, 48, 53, 50, 59, 48, 73, 56, 63, 56, 81, 54, 85, 64, 69, 68, 93, 64, 91, 70, 83, 76, 105, 72, 95, 80, 93, 86, 117, 76, 121, 92, 99, 96, 113, 86, 133, 100, 113

Offset

1,1

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Formula

a(n) = n + phi(n) = n + A000010(n).

Sum_{k=1..n} a(k) ~ c * n^2 / 2, where c = 1 + 1/zeta(2) = 1.607927... . - Amiram Eldar, Dec 16 2023

Mathematica

Table[n+EulerPhi[n], {n, 1, 70}]

Prog

(Magma) [n + EulerPhi(n): n in [1..70]]; // Vincenzo Librandi, Jul 13 2012
(PARI) a(n) = n+eulerphi(n); \\ Michel Marcus, Sep 19 2022

Crossrefs

Cf. A000010, A000040, A050530, A051953, A059956, A068080.

Sequence in context: A073673 A179217 A118809 * A075389 A053784 A036697

Adjacent sequences: A121045 A121046 A121047 * A121049 A121050 A121051

Keyword

easy,nonn

Author

Jonathan Vos Post, Aug 08 2006

Status

approved