A069949 a(n) = Sum_{d|n} phi(d+1).

1, 3, 3, 7, 3, 11, 5, 13, 7, 15, 5, 27, 7, 15, 13, 29, 7, 33, 9, 31, 17, 29, 9, 53, 15, 27, 19, 47, 9, 61, 17, 49, 23, 33, 19, 85, 19, 35, 25, 77, 13, 75, 21, 57, 39, 57, 17, 111, 25, 59, 33, 83, 19, 85, 31, 89, 39, 69, 17, 149, 31, 55, 53, 97, 29, 119, 33, 81, 35, 109, 25, 183

Offset

1,2

Links

Table of n, a(n) for n=1..72.

Formula

a(n) = Sum_{k=1..n} phi(gcd(n,k) + 1)/phi(n/gcd(n,k)). - Richard L. Ollerton, May 09 2021

Prog

(PARI) a(n)=sumdiv(n, d, eulerphi(d+1) );  /* Joerg Arndt, Sep 30 2012 */

Crossrefs

Cf. A000010.

Sequence in context: A204204 A164928 A253249 * A143275 A083262 A122978

Adjacent sequences: A069946 A069947 A069948 * A069950 A069951 A069952

Keyword

nonn

Author

Vladeta Jovovic, May 04 2002

Status

approved