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 A143317 #14 Jun 05 2023 07:08:14
%S A143317 1,3,-1,4,0,-1,7,-3,0,0,6,0,0,0,-1,12,-4,-3,0,0,1,8,0,0,0,0,0,-1,15,
%T A143317 -7,0,0,0,0,0,0,13,0,-4,0,0,0,0,0,0,18,-6,0,0,-3,0,0,0,0,1,12,0,0,0,0,
%U A143317 0,0,0,0,0,-1,28,-12,-7,0,0,3,0,0,0,0,0,0,14,0,0,0,0,0,0,0,0,0,0,0,-1
%N A143317 Triangle read by rows: A051731 * A143239.
%C A143317 Left border = sigma(n), A000203.
%C A143317 Right border = mu(n), A008683.
%C A143317 Row sums = n.
%C A143317 It appears that T(n,k) = Sum_{d|n} mu(d)*sigma(n/d). - _Joerg Arndt_, Jul 31 2011
%e A143317 First few rows of the triangle:
%e A143317 1;
%e A143317 3, -1;
%e A143317 4, 0, -1;
%e A143317 7, -3, 0, 0;
%e A143317 6, 0, 0, 0, -1;
%e A143317 12, -4, -3, 0, 0, 1;
%e A143317 8, 0, 0, 0, 0, 0, -1;
%e A143317 15, -7, 0, 0, 0, 0, 0, 0;
%e A143317 13, 0, -4, 0, 0, 0, 0, 0, 0;
%e A143317 18, -6, 0, 0, -3, 0, 0, 0, 0, 1;
%e A143317 ...
%Y A143317 Cf. A000203, A008683, A051731, A143239.
%K A143317 tabl,sign
%O A143317 1,2
%A A143317 _Gary W. Adamson_, Aug 07 2008
%E A143317 a(68) = -12 corrected by _Georg Fischer_, Jun 05 2023