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 A129691 #8 Feb 20 2022 01:27:50
%S A129691 1,-1,1,-2,0,1,-1,-1,0,1,-4,0,0,0,1,2,-2,-1,0,0,1,-6,0,0,0,0,0,1,-1,
%T A129691 -1,0,-1,0,0,0,1,-2,0,-2,0,0,0,0,0,1,4,-4,0,0,-1,0,0,0,0,1,-10,0,0,0,
%U A129691 0,0,0,0,0,0,1,2,2,-1,-2,0,-1,0,0,0,0,0,1
%N A129691 Inverse of A054523.
%C A129691 Row sums = A130054, (1, -1, -1, -3, 0, -5, -2, -3, 0, ...). A129691 * A126988 = A051731. Left column = A023900: (1, -1, -2, -1, -4, 2, -6, ...).
%H A129691 Andrew Howroyd, <a href="/A129691/b129691.txt">Table of n, a(n) for n = 1..1275</a>
%F A129691 A054523^(-1), as an infinite lower triangular matrix.
%F A129691 T(n,k) = A023900(n/k) for k | n, T(n,k) = 0 otherwise. - _Andrew Howroyd_, Aug 03 2018
%e A129691 First few rows of the triangle:
%e A129691 1;
%e A129691 -1, 1;
%e A129691 -2, 0, 1;
%e A129691 -1, -1, 0, 1;
%e A129691 -4, 0, 0, 0, 1;
%e A129691 2, -2, -1, 0, 0, 1;
%e A129691 ...
%o A129691 (PARI) T(n,k)={if(n%k, 0, sumdivmult(n/k, d, d*moebius(d)))} \\ _Andrew Howroyd_, Aug 03 2018
%Y A129691 Cf. A054523, A130055, A023900, A126988, A051731.
%K A129691 tabl,sign
%O A129691 1,4
%A A129691 _Gary W. Adamson_, May 04 2007
%E A129691 Terms a(56) and beyond from _Andrew Howroyd_, Aug 03 2018