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 A203946 #14 Feb 13 2023 05:25:33
%S A203946 1,-1,1,-2,1,1,-3,3,-1,1,-5,8,-5,1,1,-7,17,-17,7,-1,1,-9,30,-45,30,-9,
%T A203946 1,1,-11,47,-98,103,-52,12,-1,1,-13,68,-183,269,-212,83,-15,1,1,-15,
%U A203946 93,-308,588,-651,399,-123,18,-1,1,-17,122,-481,1136
%N A203946 Array: row n shows the coefficients of the characteristic polynomial of the n-th principal submatrix of A203945.
%C A203946 Let p(n)=p(n,x) be the characteristic polynomial of the n-th principal submatrix. The zeros of p(n) are positive, and they interlace the zeros of p(n+1). See A202605 for a guide to related sequences.
%D A203946 (For references regarding interlacing roots, see A202605.)
%e A203946 Top of the array:
%e A203946 1...-1
%e A203946 1...-2....1
%e A203946 1...-3....3....-1
%e A203946 1...-5....8....-5....1
%e A203946 1...-7....17...-17...7...-1
%t A203946 t = {1, 0, 0}; t1 = Flatten[{t, t, t, t, t, t, t, t, t, t}];
%t A203946 f[k_] := t1[[k]];
%t A203946 U[n_] := NestList[Most[Prepend[#, 0]] &, #,
%t A203946 Length[#] - 1] &[Table[f[k], {k, 1, n}]];
%t A203946 L[n_] := Transpose[U[n]];
%t A203946 p[n_] := CharacteristicPolynomial[L[n].U[n], x];
%t A203946 c[n_] := CoefficientList[p[n], x]
%t A203946 TableForm[Flatten[Table[p[n], {n, 1, 10}]]]
%t A203946 Table[c[n], {n, 1, 12}]
%t A203946 Flatten[%] (* A203946 *)
%t A203946 TableForm[Table[c[n], {n, 1, 10}]]
%Y A203946 Cf. A203945, A202605.
%K A203946 tabf,sign
%O A203946 1,4
%A A203946 _Clark Kimberling_, Jan 08 2012