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 A358301 #11 Apr 19 2023 09:04:56
%S A358301 2,6,20,60,124,252,388,652,924,1332,1748,2428,2988,3948,4788,5908,
%T A358301 7028,8692,9964,12052,13748,16004,18124,21204,23476,26996,29972,33788,
%U A358301 37196,42124,45548,51188,55732,61412,66532,73348,78484,86548,92956,100924,107772,117692,124556,135476,144036
%N A358301 Main diagonal of array in A358298.
%t A358301 A005728[n_] := 1 + Sum[EulerPhi[i], {i, 1, n}];
%t A358301 Amn[m_, n_] := Sum[If[GCD[i, j] == 1, 1, 0], {i, 1, m}, {j, 1, n}];
%t A358301 Dmn[m_, n_] := A005728[m] + A005728[n] + 2 Sum[d = GCD[u, v]; If[d >= 1, (u+v)*EulerPhi[d]/d, 0], {u, 1, m}, {v, 1, n}] - 2*Amn[m, n];
%t A358301 Table[Dmn[n, n], {n, 0, 44}] (* _Jean-François Alcover_, Apr 18 2023, after Maple code in A358298 *)
%Y A358301 The Farey Diagrams Farey(m,n) are studied in A358298-A358307 and A358882-A358885, the Completed Farey Diagrams of order (m,n) in A358886-A358889.
%K A358301 nonn
%O A358301 0,1
%A A358301 _Scott R. Shannon_ and _N. J. A. Sloane_, Dec 06 2022