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 A134866 #18 Dec 20 2022 11:50:18
%S A134866 1,1,1,1,3,1,1,1,1,1,1,3,4,3,1,1,1,1,1,1,1,1,3,1,7,1,3,1,1,1,4,1,1,4,
%T A134866 1,1,1,3,1,3,6,3,1,3,1,1,1,1,1,1,1,1,1,1,1,1,3,4,7,1,12,1,7,4,3,1,1,1,
%U A134866 1,1,1,1,1,1,1,1,1,1,1,3,1,3,1,3,8,3,1,3,1,3,1
%N A134866 Table read by antidiagonals: T(n,k) = sigma(gcd(n,k)).
%C A134866 Previous name was: Triangle, antidiagonals of an array formed by A051731 * A127093 (transform).
%C A134866 Row sums give A094471.
%H A134866 Michael De Vlieger, <a href="/A134866/b134866.txt">Table of n, a(n) for n = 1..11325</a> (rows n = 1..150, flattened)
%F A134866 T(n,k) = A000203(A050873(n,k)). - _Michel Marcus_, Dec 19 2022
%e A134866 First few rows of the array:
%e A134866 1, 1, 1, 1, 1, 1, 1, ...
%e A134866 1, 3, 1, 3, 1, 3, 1, ...
%e A134866 1, 1, 4, 1, 1, 4, 1, ...
%e A134866 1, 3, 1, 7, 1, 3, 1, ...
%e A134866 1, 1, 1, 1, 6, 1, 1, ...
%e A134866 ...
%e A134866 First antidiagonals:
%e A134866 1;
%e A134866 1, 1;
%e A134866 1, 3, 1;
%e A134866 1, 1, 1, 1;
%e A134866 1, 3, 4, 3, 1;
%e A134866 1, 1, 1, 1, 1, 1;
%e A134866 1, 3, 1, 7, 1, 3, 1;
%e A134866 1, 1, 4, 1, 1, 4, 1, 1;
%e A134866 1, 3, 1, 3, 6, 3, 1, 3, 1;
%e A134866 ...
%t A134866 Table[DivisorSigma[1, GCD[#, k]] &[n - k + 1], {n, 13}, {k, n}] // Flatten (* _Michael De Vlieger_, Dec 19 2022 *)
%o A134866 (PARI) T(n, k) = sigma(gcd(n, k)); \\ _Michel Marcus_, Dec 19 2022
%Y A134866 Cf. A051731, A127093, A094471, A132442.
%K A134866 nonn,tabl
%O A134866 1,5
%A A134866 _Gary W. Adamson_, Nov 14 2007
%E A134866 New name and data corrected by _Michel Marcus_, Dec 19 2022