A086899
Number of real n X n invertible symmetric (0,1) matrices.
Original entry on oeis.org
1, 4, 32, 528, 18596, 1280468, 180452552, 49970930912, 27618771417328, 30088644932329872
Offset: 1
For n = 2 the 4 matrices are 10/01, 01/10, 11/10, 01/11.
-
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}]
A086906
Number of symmetric singular n X n (0,1) matrices over the reals.
Original entry on oeis.org
1, 4, 32, 496, 14172, 816684, 87982904, 18748545824, 7565600671504, 5940152086634096
Offset: 1
Yuval Dekel (dekelyuval(AT)hotmail.com), Sep 19 2003
A118993
Number of real n X n symmetric (+1,-1) matrices with nonzero permanent.
Original entry on oeis.org
2, 4, 64, 832, 23808, 1725952, 268435456, 64638447616, 33770336417792
Offset: 1
A118989
Number of symmetric n X n (0,1)-matrices over the reals with zero permanent.
Original entry on oeis.org
1, 3, 25, 271, 6881, 254911, 20903681, 2725061631, 771426498049
Offset: 1
A119009
Number of n X n real symmetric (0,1)-matrices with permanent = 1.
Original entry on oeis.org
1, 4, 22, 286, 5126, 190096, 9477868, 923926396, 118222774300
Offset: 1
Showing 1-5 of 5 results.