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 A135669 Triangular sequence of coefficients of characteristic polynomials of a tridiagonal matrix. 5

%I

%S -1,1,-1,1,-1,1,1,-3,3,-1,1,-5,8,-5,1,1,-7,16,-16,7,-1,1,-9,27,-38,27,

%T -9,1,1,-11,41,-75,75,-41,11,-1,1,-13,58,-131,170,-131,58,-13,1,1,-15,

%U 78,-210,336,-336,210,-78,15,-1,1,-17,101,-316,602,-742,602,-316,101,-17,1

%N Triangular sequence of coefficients of characteristic polynomials of a tridiagonal matrix.

%C The first few characteristic polynomials associated with this matrix are:

%C 1 - x,

%C 1 - x + x^2,

%C (1 - x)^3,

%C (1 - x)^2*(1 - 3*x + x^2),

%C (1 - x)^3*(1 - 4*x + x^2),

%C (1 - x)^4*(1 - 5*x + x^2).

%H G. C. Greubel, <a href="/A135669/b135669.txt">Rows n = 1..100 of triangle, flattened</a>

%F With the sequence function -(n+1) the tridiagonal matrix is formed by

%F upper sub-diagonal: c(n,k) = if(n=1, -(k+1), 0),

%F diagonal: a(n,k) = if(n=1 & k > 1, -1, if(n=2, k, 1)),

%F lower sub-diagonal: b(n) = 1,

%F where the triangle is formed by t(k) = M(i, j, k) for 1 <= j <= k, 1 <= i <= k,

%F and T(n) = coefficients of CharacteristicPolynomial(M(n), x).

%e Triangle begins:

%e -1;

%e 1, -1;

%e 1, -1, 1;

%e 1, -3, 3, -1;

%e 1, -5, 8, -5, 1;

%e 1, -7, 16, -16, 7, -1;

%e 1, -9, 27, -38, 27, -9, 1;

%e 1, -11, 41, -75, 75, -41, 11, -1;

%e 1, -13, 58, -131, 170, -131, 58, -13, 1;

%e 1, -15, 78, -210, 336, -336, 210, -78, 15, -1;

%e 1, -17, 101, -316, 602, -742, 602, -316, 101, -17, 1;

%t a[n_, k_]:= If[n==1 && k > 1, -1, If[n==2, k, 1]];

%t c[n_, k_]:= If[n==1, -k-1, 0];

%t T[n_, m_, k_]:= If[n==m, a[n,k], If[n==m-1,1, If[n==m+1, c[n-1,k], 0]]];

%t M0[k_]:= Table[T[n, m, k], {n, 1, k}, {m, 1, k}];

%t TableForm[Table[M0[n], {n, 1, 4}]];

%t TableForm[Table[Inverse[M0[n]], {n, 1, 4}]];

%t Table[Factor[CharacteristicPolynomial[M0[n], x]], {n, 1, 10}];

%t Join[{{-1}}, Table[CoefficientList[CharacteristicPolynomial[M0[n], x], x], {n, 1, 10}]]//Flatten (* modified by _G. C. Greubel_, May 23 2019 *)

%K sign,tabl,less

%O 1,8

%A _Roger L. Bagula_, Feb 16 2008

%E Edited by _G. C. Greubel_, May 23 2019

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Last modified June 25 10:09 EDT 2021. Contains 345453 sequences. (Running on oeis4.)