1,3

Index entries for sequences related to binary matrices

For n = 2 the only example is the identity matrix.

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}]

Cf. A086899, A118996.

Sequence in context: A053516 A085523 A029495 this_sequence A124477 A059839 A006108

Adjacent sequences: A086897 A086898 A086899 this_sequence A086901 A086902 A086903

nonn,more

Wouter Meeussen (wouter.meeussen(AT)pandora.be) Aug 23, 2003.

a(6) and a(7) from Giovanni Resta (g.resta(AT)iit.cnr.it), May 08 2006