A086900
Number of real n X n symmetric (0,1) matrices with positive determinant.
Original entry on oeis.org
1, 1, 5, 338, 14186, 526876, 52658844, 28076946520, 18518751047608, 13637385623943256
Offset: 1
For n = 2 the only example is the identity matrix.
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triamat[li_List] := Block[{len=Sqrt[8Length[li]+1]/2-1/2}, If[IntegerQ[len], Part[li, # ]& /@ Table[If[j>i, j(j-1)/2+i, i(i-1)/2+j], {i, len}, {j, len}], li]]; 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
A118991
Number of real n X n symmetric (0,1) matrices with nonzero permanent.
Original entry on oeis.org
1, 5, 39, 753, 25887, 1842241, 247531775, 65994415105, 34412945590783
Offset: 1
A118992
Number of real n X n invertible symmetric (+1,-1) matrices.
Original entry on oeis.org
2, 4, 32, 512, 16896, 1190144, 163899904, 46195853312, 25585116626944, 28281621931343872
Offset: 1
A118996
Number of real n X n symmetric (0,1) matrices with negative determinant.
Original entry on oeis.org
0, 3, 27, 190, 4410, 753592, 127793708, 21893984392, 9100020369720, 16451259308386616
Offset: 1
A119008
Number of n X n real symmetric (0,1)-matrices with determinant = 1.
Original entry on oeis.org
1, 1, 4, 268, 9456, 301306, 24846368, 8946957244, 4175660906560, 2421067614753916
Offset: 1
Showing 1-7 of 7 results.