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 A071548 #2 Mar 30 2012 17:30:44
%S A071548 0,-1,2,0,0,0,2,1,-4,12,0,-12,-4,7,44,48,0,-48,44,345,334,-1196,2328,
%T A071548 4796,8022,-35417,123840,-118503,89082,48160,-414248,2107104,-2358342,
%U A071548 -27802725,-168156872,415198413,804518348,-2450715149,-711441100,3648319725,-2721771200,-17289389524,205130688
%N A071548 Determinant of the n X n matrix whose element (i,j) equals f(|i-j|) where f(n) is 1 if the sum of middle divisors (A071090) > 0, else 0.
%t A071548 f[n_] := If[n > 0, If[Plus @@ Select[ Divisors[n], Sqrt[n/2] <= # < Sqrt[n*2] &] == 0, 0, 1], 0]; Table[ Det[ Table[ f[ Abs[i - j]], {i, 1, n}, {j, 1, n}]], {n, 1, 50}]
%Y A071548 Cf. A071090.
%K A071548 sign
%O A071548 1,3
%A A071548 _Robert G. Wilson v_, May 30 2002