This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A372661 #23 May 09 2024 12:21:57
%S A372661 1,14,98,412,1436,3212,8312,17460,34182,57406,107306,161942,277550,
%T A372661 406490,581210,850162,1292018,1701752,2481476,3216100,4184464,5406704,
%U A372661 7414512,9119640,11849180,14736284,18541664,22500200,28950168,33410736,42380976,51166240,60859420
%N A372661 a(n) = Sum_{i=1..n} Sum_{j=1..n} Sum_{k=1..n} phi(i*j*k).
%H A372661 Vaclav Kotesovec, <a href="/A372661/b372661.txt">Table of n, a(n) for n = 1..1000</a>
%H A372661 Vaclav Kotesovec, <a href="/A372661/a372661.jpg">Plot of a(n)/n^6 for n = 1..1000</a>
%H A372661 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/TotientFunction.html">Totient Function</a>.
%t A372661 Table[Sum[EulerPhi[i*j*k], {i, 1, n}, {j, 1, n}, {k, 1, n}], {n, 1, 40}] (* _Vaclav Kotesovec_, May 09 2024 *)
%t A372661 s = 1; Join[{1}, Table[s += Sum[EulerPhi[i*j*n], {i, 1, n}, {j, 1, n}] + Sum[EulerPhi[i*j*n], {i, 1, n - 1}, {j, 1, n}] + Sum[EulerPhi[i*j*n], {i, 1, n - 1}, {j, 1, n - 1}], {n, 2, 40}]] (* _Vaclav Kotesovec_, May 09 2024 *)
%o A372661 (PARI) a(n) = sum(i=1, n, sum(j=1, n, sum(k=1, n, eulerphi(i*j*k))));
%Y A372661 Cf. A000010, A372633, A372662, A372663.
%K A372661 nonn
%O A372661 1,2
%A A372661 _Seiichi Manyama_, May 09 2024