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%I #14 May 10 2024 04:17:15
%S 1,14,72,271,731,1649,3417,6654,11495,18635,29971,45088,67562,95862,
%T 129315,180548,247178,324463,429785,547025,679318,853788,1080248,
%U 1324791,1617620,1964622,2361036,2813206,3392778,3946537,4704245,5550066,6389704,7421750,8455877
%N a(n) = Sum_{i=1..n} Sum_{j=1..n} Sum_{k=1..n} phi(i*j*k) / phi(k).
%H Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/TotientFunction.html">Totient Function</a>.
%t Table[Sum[EulerPhi[i*j*k]/EulerPhi[k], {i, 1, n}, {j, 1, n}, {k, 1, n}], {n, 1, 40}] (* _Vaclav Kotesovec_, May 10 2024 *)
%o (PARI) a(n) = sum(i=1, n, sum(j=1, n, sum(k=1, n, eulerphi(i*j*k)/eulerphi(k))));
%Y Cf. A000010, A372636, A372661, A372663.
%K nonn
%O 1,2
%A _Seiichi Manyama_, May 09 2024