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Partial sums of A007694.
4

%I #10 Nov 05 2024 03:10:47

%S 1,3,7,13,21,33,49,67,91,123,159,207,261,325,397,493,601,729,873,1035,

%T 1227,1443,1699,1987,2311,2695,3127,3613,4125,4701,5349,6117,6981,

%U 7953,8977,10129,11425,12883,14419,16147,18091,20139,22443,25035,27951,31023

%N Partial sums of A007694.

%C Partial sums of numbers k such that phi(k) divides k.

%H Amiram Eldar, <a href="/A174030/b174030.txt">Table of n, a(n) for n = 1..1000</a>

%F a(n) = Sum_{i=1..n} A007694(i).

%F a(n) = 2*A259823(n-1) + 1. - _Amiram Eldar_, Nov 05 2024

%t Accumulate[Select[Range[5000], Divisible[#, EulerPhi[#]] &]] (* _Amiram Eldar_, Nov 05 2024 *)

%Y Cf. A000010, A007694, A259823.

%K nonn

%O 1,2

%A _Jonathan Vos Post_, Mar 06 2010