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a(n) = (1/phi(n)) * Sum_{j=1..n} Sum_{k=1..n} phi(n*j*k).
1

%I #8 May 10 2024 03:43:42

%S 1,9,26,83,132,404,400,989,1199,2382,2096,5381,3922,8358,8525,12897,

%T 10758,25517,16618,34116,30217,45156,34224,77503,50559,87512,77328,

%U 119162,84364,198907,108928,196605,174258,249884,195499,374490,215930,386822,330878,500717

%N a(n) = (1/phi(n)) * Sum_{j=1..n} Sum_{k=1..n} phi(n*j*k).

%t Table[Sum[EulerPhi[n*j*k], {j, 1, n}, {k, 1, n}]/EulerPhi[n], {n, 1, 40}] (* _Vaclav Kotesovec_, May 10 2024 *)

%o (PARI) a(n) = sum(j=1, n, sum(k=1, n, eulerphi(n*j*k)))/eulerphi(n);

%Y Cf. A000010, A070639, A372669.

%K nonn

%O 1,2

%A _Seiichi Manyama_, May 09 2024