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 A128407 #13 Feb 18 2022 22:15:41
%S A128407 1,0,-1,0,0,-1,0,0,0,0,0,0,0,0,-1,0,0,0,0,0,1,0,0,0,0,0,0,-1,0,0,0,0,
%T A128407 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1
%N A128407 Triangle read by rows: T(n,n) = mobius(n) on the diagonal, zero elsewhere.
%C A128407 A128407 * [1,2,3,...] = n*mu(n), A055615: (1, -2, -3, 0, -5, 6, -7, 0, ...). A051731 * A128407 = A054524. A128407 * A051731 = A128408.
%H A128407 Harvey P. Dale, <a href="/A128407/b128407.txt">Table of n, a(n) for n = 1..1000</a>
%F A128407 Infinite lower triangular matrix with mu(n), A008683, as the right border and the rest zeros.
%e A128407 First few rows of the triangle:
%e A128407 1;
%e A128407 0, -1;
%e A128407 0, 0, -1;
%e A128407 0, 0, 0, 0;
%e A128407 0, 0, 0, 0, -1;
%e A128407 0, 0, 0, 0, 0, 1;
%e A128407 0, 0, 0, 0, 0, 0, -1;
%e A128407 ...
%t A128407 Table[PadLeft[{MoebiusMu[n]},n],{n,10}]//Flatten (* _Harvey P. Dale_, Dec 29 2021 *)
%Y A128407 Cf. A051731, A128408, A008683 (row sums and diagonal), A054524.
%K A128407 tabl,sign,easy
%O A128407 1,1
%A A128407 _Gary W. Adamson_, Mar 01 2007
%E A128407 Name improved . - _R. J. Mathar_, Aug 03 2015