A204181 Symmetric matrix based on f(i,j) defined by f(i,1)=f(1,j)=1; f(i,i)= 2i-1; f(i,j)=0 otherwise; by antidiagonals.

1, 1, 1, 1, 3, 1, 1, 0, 0, 1, 1, 0, 5, 0, 1, 1, 0, 0, 0, 0, 1, 1, 0, 0, 7, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 9, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 11, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 13, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0

Offset

1,5

Comments

A204181 represents the matrix M given by f(i,j) for i>=1 and j>=1. See A204182 for characteristic polynomials of principal submatrices of M, with interlacing zeros. See A204016 for a guide to other choices of M.

Links

Table of n, a(n) for n=1..98.

Example

Northwest corner:
1 1 1 1 1 1 1 1
1 3 0 0 0 0 0 0
1 0 5 0 0 0 0 0
1 0 0 7 0 0 0 0
1 0 0 0 9 0 0 0

Mathematica

f[i_, j_] := 0; f[1, j_] := 1;
f[i_, 1] := 1; f[i_, i_] := 2 i - 1;
m[n_] := Table[f[i, j], {i, 1, n}, {j, 1, n}]
TableForm[m[8]] (* 8x8 principal submatrix *)
Flatten[Table[f[i, n + 1 - i],
  {n, 1, 15}, {i, 1, n}]]  (* A204181 *)
p[n_] := CharacteristicPolynomial[m[n], x];
c[n_] := CoefficientList[p[n], x]
TableForm[Flatten[Table[p[n], {n, 1, 10}]]]
Table[c[n], {n, 1, 12}]
Flatten[%]                 (* A204182 *)
TableForm[Table[c[n], {n, 1, 10}]]

Crossrefs

Cf. A204182, A204016, A202453.

Sequence in context: A350879 A115718 A361510 * A204242 A211313 A368847

Adjacent sequences: A204178 A204179 A204180 * A204182 A204183 A204184

Keyword

nonn,tabl

Author

Clark Kimberling, Jan 12 2012

Status

approved