Please help, I searched the text several times but could not figure out how to solve this problem(Wondering)

How many 6 x 6(0,1)-matricesAare there withA =A^tr?

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- January 14th 2013, 05:08 AMwattskickincalculate matrices
Please help, I searched the text several times but could not figure out how to solve this problem(Wondering)

How many 6 x 6*(*0*,*1*)*-matrices*A*are there with*A =**A^*tr? - January 14th 2013, 05:37 AMemakarovRe: calculate matrices
Maybe you can find first how many symmetric 2 x 2 and 3 x 3 (0, 1)-matrices there are.

- January 14th 2013, 05:48 AMkalyanramRe: calculate matrices
I hope this is what you mean.

How many 6x6 matrices can be there such that . Elements of the matrices can be selected from the set ?

Sol: For we need where is the element in the row column.

We consider the elements where (why ?). There are 21 such elements and for each of these elements we have 2 choices so we have such matrices.

Kalyan.