A204018 Symmetric matrix based on f(i,j)=1+max(j mod i, i mod j), by antidiagonals.

1, 2, 2, 2, 1, 2, 2, 3, 3, 2, 2, 3, 1, 3, 2, 2, 3, 4, 4, 3, 2, 2, 3, 4, 1, 4, 3, 2, 2, 3, 4, 5, 5, 4, 3, 2, 2, 3, 4, 5, 1, 5, 4, 3, 2, 2, 3, 4, 5, 6, 6, 5, 4, 3, 2, 2, 3, 4, 5, 6, 1, 6, 5, 4, 3, 2, 2, 3, 4, 5, 6, 7, 7, 6, 5, 4, 3, 2, 2, 3, 4, 5, 6, 7, 1, 7, 6, 5, 4, 3, 2, 2, 3, 4, 5, 6, 7, 8, 8

Offset: 1

Author

Clark Kimberling, Jan 11 2012

Keywords

• nonn
• tabl

Comments

A204018 represents the matrix M given by f(i,j)=max{1+(j mod i), 1+( i mod j)} for i>=1 and j>=1. See A204019 for characteristic polynomials of principal submatrices of M, with interlacing zeros. See A204016 for a guide to other choices of M.

Examples

			Northwest corner:
1 2 2 2 2 2
2 1 3 3 3 3
2 3 1 4 4 4
2 3 4 1 5 5
2 3 4 5 1 6
2 3 4 5 6 1
		

Crossrefs

Cf. A204019, A204016, A202453.

Programs

Mathematica

f[i_, j_] := 1 + Max[Mod[i, j], Mod[j, i]];
m[n_] := Table[f[i, j], {i, 1, n}, {j, 1, n}]
TableForm[m[6]] (* 6x6 principal submatrix *)
Flatten[Table[f[i, n + 1 - i],
  {n, 1, 15}, {i, 1, n}]]   (* A204018 *)
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[%]                  (* A204019 *)
TableForm[Table[c[n], {n, 1, 10}]]