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A364230
Triangle read by rows: T(n, k) is the number of n X n symmetric Toeplitz matrices of rank k using all the integers 1, 2, ..., n.
1
1, 0, 2, 0, 0, 6, 0, 0, 0, 24, 0, 0, 0, 0, 120, 0, 0, 0, 0, 2, 718, 0, 0, 0, 0, 4, 31, 5005, 0, 0, 0, 0, 0, 2, 44, 40274, 0, 0, 0, 0, 0, 0, 4, 272, 362604, 0, 0, 0, 0, 0, 0, 0, 111, 774, 3627915, 0, 0, 0, 0, 0, 0, 2, 14, 244, 6974, 39909566, 0, 0, 0, 0, 0, 0, 0, 4, 64, 743, 9533, 478991256
OFFSET
1,3
EXAMPLE
The triangle begins:
1;
0, 2;
0, 0, 6;
0, 0, 0, 24;
0, 0, 0, 0, 120;
0, 0, 0, 0, 2, 718;
0, 0, 0, 0, 4, 31, 5005;
...
MATHEMATICA
T[n_, k_]:= Count[Table[MatrixRank[ToeplitzMatrix[Part[Permutations[Range[n]], i]]], {i, n!}], k]; Table[T[n, k], {n, 8}, {k, n}]//Flatten
PROG
(PARI)
MkMat(v)={matrix(#v, #v, i, j, v[1+abs(i-j)])}
row(n)={my(f=vector(n)); forperm(vector(n, i, i), v, f[matrank(MkMat(v))]++); f} \\ Andrew Howroyd, Dec 30 2023
CROSSREFS
Cf. A000142 (row sums), A350953 (minimal determinant), A350954 (maximal determinant), A351019 (minimal permanent), A351020 (maximal permanent), A356865 (minimal nonzero absolute value determinant), A364231 (right diagonal).
Sequence in context: A106512 A181229 A364233 * A259857 A364790 A094785
KEYWORD
nonn,tabl
AUTHOR
Stefano Spezia, Jul 14 2023
EXTENSIONS
Terms a(46) and beyond from Andrew Howroyd, Dec 30 2023
STATUS
approved