Number of symmetric reflexive relations on n nodes: (1/2)*A000666.

A000250

Number of symmetric reflexive relations on n nodes: (1/2)*A000666.

Terms

    a(0) =1a(1) =3a(2) =10a(3) =45a(4) =272a(5) =2548a(6) =39632a(7) =1104306a(8) =56871880a(9) =5463113568a(10) =978181717680

External references