|
| |
|
|
A086899
|
|
Number of real n X n invertible symmetric (0,1) matrices.
|
|
5
| | |
|
|
|
OFFSET
| 1,2
|
|
|
LINKS
| Index entries for sequences related to binary matrices
|
|
|
EXAMPLE
| For n = 2 the 4 matrices are 10/01, 01/10, 11/10, 01/11.
|
|
|
MATHEMATICA
| triamat[li_List] := (*see A086900*); Table[it=triamat/@IntegerDigits[Range[0, -1+2^(n(n+1)/2)], 2, n(n+1)/2]; Count[it, (q_)?MatrixQ/; (Det[q]=!=0)], {n, 5}]
|
|
|
CROSSREFS
| Cf. A086900, A086906, A118991.
Sequence in context: A036442 A127945 A186339 * A013041 A006024 A118995
Adjacent sequences: A086896 A086897 A086898 * A086900 A086901 A086902
|
|
|
KEYWORD
| nonn,more
|
|
|
AUTHOR
| Wouter Meeussen (wouter.meeussen(AT)pandora.be) Aug 23, 2003.
|
|
|
EXTENSIONS
| a(6) and a(7) from Giovanni Resta (g.resta(AT)iit.cnr.it), May 08 2006
|
| |
|
|
