A123973 Sequence of tridiagonal matrices with one center zero terminal that give a triangular sequence from the characteristic polynomials based on the 3 X 3 matrix type: {{1, -1, 0}, {-1, 1, -1}, {0, -1, 0}}.

0, 0, -1, -1, -1, 1, -1, 1, 2, -1, 0, 3, 0, -3, 1, 1, 2, -5, -2, 4, -1, 1, -2, -7, 6, 5, -5, 1, 0, -5, 0, 15, -5, -9, 6, -1, -1, -3, 12, 9, -25, 1, 14, -7, 1, -1, 3, 15, -18, -29, 35, 7, -20, 8, -1, 0, 7, 0, -42, 14, 63, -42, -20, 27, -9, 1

Offset

1,9

Comments

Matrices: {{0}}, {{1, -1}, {-1, 0}}, {{1, -1, 0}, {-1, 1, -1}, {0, -1, 0}}, {{1, -1, 0, 0}, {-1, 1, -1, 0}, {0, -1, 1, -1}, {0, 0, -1, 0}}, {{1, -1, 0, 0, 0}, {-1, 1, -1, 0, 0}, {0, -1, 1, -1, 0}, {0, 0, -1, 1, -1}, {0, 0, 0, -1, 0}}, {{1, -1, 0, 0, 0, 0}, {-1, 1, -1, 0, 0, 0}, {0, -1, 1, -1, 0, 0}, {0, 0, -1, 1, -1, 0}, { 0, 0, 0, -1, 1, -1}, {0, 0, 0, 0, -1, 0}} Determinants ( not all Sl(3,Z) and invertable): Table[Det[M[d]], {d, 1, 10}] {0, -1, -1, 0, 1, 1, 0, -1, -1, 0}

Links

Table of n, a(n) for n=1..66.

Formula

t(n,m,d)=If[ n == m && n < d && m < d, 1, If[n == m - 1 || n == m + 1, -1, If[n == m == d, 0, 0]]]

Example

Triangle begins:
{0},
{0, -1},
{-1, -1, 1},
{-1, 1, 2, -1},
{0, 3, 0, -3, 1},
{1, 2, -5, -2, 4, -1},
{1, -2, -7, 6, 5, -5, 1},
{0, -5, 0, 15, -5, -9, 6, -1},
{-1, -3, 12, 9, -25, 1, 14, -7, 1},
{-1, 3, 15, -18, -29, 35,7, -20, 8, -1},
{0, 7, 0, -42, 14, 63, -42, -20, 27, -9, 1}
Some of the polynomials are Steinbach.

Mathematica

T[n_, m_, d_] := If[ n == m && n < d && m < d, 1, If[n == m - 1 || n == m + 1, -1, If[n == m == d, 0, 0]]] M[d_] := Table[T[n, m, d], {n, 1, d}, {m, 1, d}] Table[M[d], {d, 1, 10}] Table[Det[M[d]], {d, 1, 10}] Table[Det[M[d] - x*IdentityMatrix[d]], {d, 1, 10}] a = Join[M[1], Table[CoefficientList[Det[M[ d] - x*IdentityMatrix[d]], x], {d, 1, 10}]] Flatten[a] MatrixForm[a]

Crossrefs

Sequence in context: A178780 A058558 A210869 * A098493 A058560 A131047

Adjacent sequences: A123970 A123971 A123972 * A123974 A123975 A123976

Keyword

uned,tabl,sign

Author

Gary W. Adamson and Roger L. Bagula, Oct 30 2006

Extensions

Looking at the triangle suggests that the very first term should be 1, not 0, see A098493. - N. J. A. Sloane, Nov 01 2006

Status

approved