Number of n X n symmetric binary matrices containing no more than two 1s in any 2 X 2 sub-block.

A139007

Number of n X n symmetric binary matrices containing no more than two 1s in any 2 X 2 sub-block.

Terms

    a(0) =1a(1) =2a(2) =5a(3) =25a(4) =205a(5) =2849a(6) =66677a(7) =2633485a(8) =175143651a(9) =19638725775

External references