

A086899


Number of real n X n invertible symmetric (0,1) matrices.


5




OFFSET

1,2


LINKS



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



KEYWORD

nonn,more


AUTHOR



EXTENSIONS



STATUS

approved



