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 A155031 #13 Mar 08 2021 04:33:14
%S A155031 1,0,1,0,-1,1,0,0,-1,1,0,-1,-1,-1,1,0,0,0,-1,-1,1,0,-1,-1,-1,-1,-1,1,
%T A155031 0,0,-1,0,-1,-1,-1,1,0,-1,0,-1,-1,-1,-1,-1,1,0,0,-1,-1,0,-1,-1,-1,-1,
%U A155031 1,0,-1,-1,-1,-1,-1,-1,-1,-1,-1,1,0,0,0,0,-1,0,-1,-1,-1,-1,-1,1,0,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,1
%N A155031 Triangle T(n, k) = 0 if n==0 (mod k) otherwise -1 with T(n, n) = 1 and T(n, 0) = 0, read by rows.
%H A155031 G. C. Greubel, <a href="/A155031/b155031.txt">Rows n = 1..30 of the triangle, flattened</a>
%F A155031 T(n, k) = A154990(n, k) * A155029(n, k).
%F A155031 T(n, k) = 0 if n==0 (mod k) otherwise -1 with T(n, n) = 1 and T(n, 0) = 0.
%e A155031 Table begins:
%e A155031 1;
%e A155031 0, 1;
%e A155031 0, -1, 1;
%e A155031 0, 0, -1, 1;
%e A155031 0, -1, -1, -1, 1;
%e A155031 0, 0, 0, -1, -1, 1;
%e A155031 0, -1, -1, -1, -1, -1, 1;
%e A155031 0, 0, -1, 0, -1, -1, -1, 1;
%e A155031 0, -1, 0, -1, -1, -1, -1, -1, 1;
%t A155031 T[n_, k_]:= If[k==n, 1, If[k==1 || Mod[n, k]==0, 0, -1]];
%t A155031 Table[T[n, k], {n, 12}, {k, n}] //Flatten (* _G. C. Greubel_, Mar 08 2021 *)
%o A155031 (Sage) flatten([[1 if k==n else 0 if (k==1 or n%k==0) else -1 for k in [1..n]] for n in [1..12]]) # _G. C. Greubel_, Mar 08 2021
%o A155031 (Magma) [k eq n select 1 else (k eq 1 or n mod k eq 0) select 0 else -1: k in [1..n], n in [1..12]]; // _G. C. Greubel_, Mar 08 2021
%Y A155031 Cf. A154990, A155029.
%K A155031 sign,tabl
%O A155031 1,1
%A A155031 _Mats Granvik_, Jan 19 2009