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

%I #12 May 09 2021 08:09:51

%S 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,

%T 47,9,61,17,49,23,33,19,85,19,35,25,77,13,75,21,57,39,57,17,111,25,59,

%U 33,83,19,85,31,89,39,69,17,149,31,55,53,97,29,119,33,81,35,109,25,183

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

%F a(n) = Sum_{k=1..n} phi(gcd(n,k) + 1)/phi(n/gcd(n,k)). - _Richard L. Ollerton_, May 09 2021

%o (PARI) a(n)=sumdiv(n, d, eulerphi(d+1) ); /* _Joerg Arndt_, Sep 30 2012 */

%Y Cf. A000010.

%K nonn

%O 1,2

%A _Vladeta Jovovic_, May 04 2002

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Last modified May 25 04:52 EDT 2024. Contains 372782 sequences. (Running on oeis4.)