A209187 Sum of divisors of n minus cototient of n.

1, 2, 3, 5, 5, 8, 7, 11, 10, 12, 11, 20, 13, 16, 17, 23, 17, 27, 19, 30, 23, 24, 23, 44, 26, 28, 31, 40, 29, 50, 31, 47, 35, 36, 37, 67, 37, 40, 41, 66, 41, 66, 43, 60, 57, 48, 47, 92, 50, 63, 53, 70, 53, 84, 57, 88, 59, 60, 59, 124, 61, 64, 77, 95, 67, 98, 67, 90, 71, 98, 71

Offset

1,2

Links

Ivan Neretin, Table of n, a(n) for n = 1..10000

PrimeFan, Listing of Esoteric Integer Sequences.

Formula

a(n) = A065387(n) - n. - Altug Alkan, Sep 30 2017

a(n) = A000203(n) - A051953(n). - Omar E. Pol, Sep 30 2017

Sum_{k=1..n} a(k) = c * n^2 / 2 + O(n*log(n)), where c = 6/Pi^2 + Pi^2/6 - 1 = 1.252861... . - Amiram Eldar, Dec 08 2023

Mathematica

Table[(Plus @@ Divisors[n]) - (n - EulerPhi[n]), {n, 50}]

Prog

(PARI) a(n) = sigma(n) + eulerphi(n) - n; \\ Altug Alkan, Sep 30 2017

Crossrefs

Cf. A000203, A051953, A065387.

Cf. A013661, A059956.

Sequence in context: A134871 A267453 A063914 * A357259 A166250 A174088

Adjacent sequences: A209184 A209185 A209186 * A209188 A209189 A209190

Keyword

nonn,easy

Author

N. J. A. Sloane, Mar 05 2012

Status

approved