Number of symmetric relations on n nodes.

A000666

Number of symmetric relations on n nodes.

Terms

    a(0) =1a(1) =2a(2) =6a(3) =20a(4) =90a(5) =544a(6) =5096a(7) =79264a(8) =2208612a(9) =113743760a(10) =10926227136

External references