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 A204122 #10 Aug 02 2019 04:13:05
%S A204122 1,-1,1,-3,1,2,-8,7,-1,8,-36,43,-15,1,64,-304,414,-198,31,-1,1024,
%T A204122 -4992,7224,-3960,849,-63,1,32768,-161792,241088,-140864,34674,-3516,
%U A204122 127,-1,2097152,-10420224,15752192,-9492480,2493640,-290412
%N A204122 Array: row n shows the coefficients of the characteristic polynomial of the n-th principal submatrix of f(i,j) = gcd(2^(i-1), 2^(j-1)) (A144464).
%C A204122 Let p(n)=p(n,x) be the characteristic polynomial of the n-th principal submatrix. The zeros of p(n) are real, and they interlace the zeros of p(n+1). See A202605 and A204016 for guides to related sequences.
%D A204122 (For references regarding interlacing roots, see A202605.)
%e A204122 Top of the array:
%e A204122 1, -1;
%e A204122 1, -3, 1;
%e A204122 2, -8, 7, -1;
%e A204122 8, -36, 43, -15, 1;
%t A204122 f[i_, j_] := GCD[2^(i - 1), 2^(j - 1)];
%t A204122 m[n_] := Table[f[i, j], {i, 1, n}, {j, 1, n}]
%t A204122 TableForm[m[8]] (* 8 X 8 principal submatrix *)
%t A204122 Flatten[Table[f[i, n + 1 - i],
%t A204122 {n, 1, 15}, {i, 1, n}]] (* A144464 *)
%t A204122 p[n_] := CharacteristicPolynomial[m[n], x];
%t A204122 c[n_] := CoefficientList[p[n], x]
%t A204122 TableForm[Flatten[Table[p[n], {n, 1, 10}]]]
%t A204122 Table[c[n], {n, 1, 12}]
%t A204122 Flatten[%] (* A204122 *)
%t A204122 TableForm[Table[c[n], {n, 1, 10}]]
%Y A204122 Cf. A144464, A202605, A204016.
%K A204122 tabl,sign
%O A204122 1,4
%A A204122 _Clark Kimberling_, Jan 11 2012