A111749 Number of (-1,0,1) periodic irreducible matrices (with Tij=-Tji for i<j) up to sign change, transposition and row and column permutations.

1, 3, 10, 39, 121, 405

Offset

1,2

Comments

The permutations of rows i anf j, followed by those of column i and j, preserve the property that (Tij=-Tji for i<j). The periods of the 405 6 X 6 matrices are: 11 times period 3, 94 times period 4, 71 times period 6 and 229 times period 12.

Links

Table of n, a(n) for n=1..6.

Wouter Meeussen, Periodic Matrices

Example

{{-1,-1,0,0,0,0},{1,1,-1,0,0,0},{0,1,-1,0,0,0},{0,0,0,-1,-1,0},{0,0,0,1,1,-1},{0,0,0,0,1,-1}} is one of the 6 by 6 matrices.

Mathematica

see link.

Crossrefs

Cf. A072148, A111485.

Sequence in context: A259859 A298940 A327847 * A149048 A149049 A149050

Adjacent sequences: A111746 A111747 A111748 * A111750 A111751 A111752

Keyword

hard,nonn

Author

Wouter Meeussen, Nov 19 2005

Status

approved