A204002 - OEIS

A204002

Symmetric matrix based on f(i,j)=min{2i+j,i+2j}, by antidiagonals.

3, 4, 4, 5, 6, 5, 6, 7, 7, 6, 7, 8, 9, 8, 7, 8, 9, 10, 10, 9, 8, 9, 10, 11, 12, 11, 10, 9, 10, 11, 12, 13, 13, 12, 11, 10, 11, 12, 13, 14, 15, 14, 13, 12, 11, 12, 13, 14, 15, 16, 16, 15, 14, 13, 12, 13, 14, 15, 16, 17, 18, 17, 16, 15, 14, 13, 14, 15, 16, 17, 18, 19, 19

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OFFSET

1,1

COMMENTS

A204002 represents the matrix M given by f(i,j)=min{2i+j,i+2j}for i>=1 and j>=1. See A204003 for characteristic polynomials of principal submatrices of M, with interlacing zeros.

LINKS

Table of n, a(n) for n=1..73.

EXAMPLE

Northwest corner:

3...4...5....6....7....8

4...6...7....8....9....10

5...7...9....10...11...12

6...8...10...12...13...14

MATHEMATICA

f[i_, j_] := Min[2 i + j, 2 j + i];

m[n_] := Table[f[i, j], {i, 1, n}, {j, 1, n}]

TableForm[m[6]] (* 6x6 principal submatrix *)